Cross Section - Department of Transport and Main Roads

September 2004 i

Road Planning and Design Manual Chapter 7: Cross Section

7Chapter 7

Cross Section

ii September 2004

Chapter 7: Cross Section Road Planning and Design Manual

7

Table of ContentsAcknowledgement 7-1

7.1 Introduction 7-17.1.1 General 7-17.1.2 Cross Section Determination 7-27.1.3 Terminology 7-2

7.2 Lanes 7-67.2.1 General 7-67.2.2 Two Lane Two Way Rural Roads 7-77.2.3 Multilane Rural Roads and Motorways 7-87.2.4 Urban Roads 7-87.2.5 National Highways 7-87.2.6 Bus Routes 7-87.2.7 Auxiliary Lanes 7-97.2.8 Parking Lanes 7-97.2.9 Turning Lanes/Turning Roadways and Ramps 7-107.2.10 Cycleways 7-117.2.11 Location of Kerb and/or Channels 7-127.2.12 Transit Lanes 7-12

7.3 Shoulders 7-207.3.1 General 7-207.3.2 Two Lane Two Way Rural Roads 7-207.3.3 Multilane Rural Roads and Motorways 7-217.3.4 Auxiliary Lanes 7-217.3.5 Ramps 7-217.3.6 Urban Roads 7-227.3.7 National Highways 7-227.3.8 Cycleways 7-227.3.9 Change in Shoulder Width 7-23

7.4 Medians 7-237.4.1 General 7-237.4.2 Rural Roads 7-237.4.3 Urban Roads 7-247.4.4 Motorways 7-267.4.5 Clearance to Medians 7-267.4.6 Rural Median Treatment 7-26

7.5 Verges, Footpaths and Outer Separators 7-277.5.1 Verges 7-277.5.2 Footpaths 7-277.5.3 Outer Separators 7-32

7.6 Clear Zone 7-367.6.1 General 7-367.6.2 Guidelines 7-36

7.7 Crossfall 7-367.7.1 General 7-367.7.2 Crossfall and Drainage 7-387.7.3 Road Crossfall 7-387.7.4 Median Crossfall 7-39

September 2004 iii


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7.7.5 Footpath Crossfall 7-397.7.6 Parking Lane Crossfall 7-397.7.7 Crossfall Configuration on Side Slopes 7-397.7.8 Split Level Carriageways 7-40

7.8 Batters 7-417.8.1 Batter Slopes 7-417.8.2 Traversable Batters and Batter Rounding 7-427.8.3 Batter Slope Treatment 7-437.8.4 Benches 7-437.8.5 Rock Fall Protection 7-48

7.9 Drainage 7-487.9.1 Table Drains 7-487.9.2 Catch Drains and Banks 7-487.9.3 Dykes 7-507.9.4 Batter Drains 7-507.9.5 Kerbs, Channels and Access Chambers 7-507.9.6 Floodways 7-51

7.10 Bridges and Clearances 7-537.10.1 Road Bridge Widths 7-537.10.2 Pedestrian/Cyclist Bridges 7-597.10.3 Lateral Clearance 7-597.10.4 Vertical Clearance 7-607.10.5 Pedestrian/Cyclist Subways 7-617.10.6 Clearance to Railways 7-617.10.7 Public Utility Plant 7-62

7.11 Special Considerations 7-627.11.1 Roads on Expansive Soils in Western Queensland 7-627.11.2 Roads in Rainforest (including Wet Tropics) 7-67

7.12 Typical Cross Sections 7-71

References 7-80

Relationship to Other Chapters 7-81

Appendix 7A: Template for Vehicle Clearance at Property Entrances 7-82

Appendix 7B:Multi-Combination Vehicles in Urban Areas 7-83

iv September 2004


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September 2004 v


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Chapter 7 Amendments - September 2004

Revision Register

Issue/ Reference Description of Revision Authorised DateRev No. Section by

1 First Issue Steering Aug 2000Committee

2 7.2.12 New section7.5.2 Footpaths and Driveways - modification to W. Semple Jan 2001

2nd paragraph3 7.2.8 Modification to 1st paragraph W. Semple Feb 2001

7.10.1 Table 7.18 - modification to notes4 7.1.3 Additional definition

7.2.4 Modifications. Table 7.5 removed7.2.6 Modifications7.2.8 Modifications7.2.10 Modifications7.2.11 Additional dot point7.5.2 Additions7.7.3 Additional subsection Steering July7.7.5 ‘Sight impaired’ changed to ‘visually impaired’. Committee 20017.7.6 Additional subsection7.9.2 Figure 7.20 modified. Additions to 3rd paragraph7.9.5 Modifications and additions. Figure 7.21 modified7.9.6 New7.10.1 Additional 2nd paragraph7.10.2 Modifications to 1st paragraph re min. vertical clearance7.10.4 Modifications to Table 7.217.10.5 Additional paragraphNew Relationship to other chapters

5 7.2.1 Diagram renumbered as Figure 7.2.1 and referenced in text7.2.12 New subsection “Enforcement”. Modifications to Figures

7.2.12.5 to 7.2.12.87.4.2 Additional text after 3rd paragraph7.4.6 Additional text at the end of 1st paragraph7.5.2 Modifications to Figures 7.7 Steering May7.9.5 Additional text at the beginning of subsection Committee 20027.10.1 Additional text after 3rd paragraph7.10.2 Additional text7.10.7 Modifications to Table 7.227.12 Modifications to Figures 7.27 to 7.29 and 7.32App. 7A Modifications to diagram

6 7.3.9 New section - “Change in Shoulder Width” Steering July7.4.3 Additional text - “Tips for treatment of urban medians” Committee 20027.7.3 Additional text - limits on crossfall for turning roadways

7 7.2.4 Inclusion of Chapter no. for reference7.2.8 Additional text “Parking restrictions at intersections” Steering Sep7.2.11 Correction of section reference number Committee 20047.2.12 Additional text - “Transit Lanes - Enforcement”

vi September 2004

Issue/ Reference Description of Revision Authorised DateRev No. Section by

7 7.3.1 Correction of table reference number Steering Sep7.4.3 Additional text - “Urban Roads - Tips for treatment of Committee 2004

urban medians”7.4.3 Correction of typical/cross sections reference number7.4.5 Correction to kerb type reference numbers7.4.6 Spelling correction7.4.6 Correction to Typical Cross Section reference number7.5 Modifications to Fig 7.77.5.2 Correction to text7.5.2 Additional text7.5.2 Removal of reference to Fig 7.147.5.2 Move text7.6 Additional symbol on Fig 7.127.6.2 Additional text7.7.1 Spelling correction7.7.3 Additional text - inclusion of Chapter no. for reference7.7 Additional text as 7.7.67.7.6 Renumbered to 7.7.77.7.7 Renumbered to 7.7.87.8 Modification to Fig 7.18(b) - spelling error7.9.1 Correction to kerb type numbers7.9.5 Change of Table 7.9.6 to Table 7.167.9 Fig 7.21 - correction of dimension in type 3 kerb7.9 Fig 7.21 - Additional note for kerb type 25/267.9 Fig 7.21 - Additional note for kerb type 18/19/20/217.9 Fig 7.21 - Removal of kerb types 28 and 297.9 Fig 7.21 - Rename kerb type 30 to type 287.9.6 Amendment to table number - “Width Range”7.9.6 Removal of text - “Width Range”7.10.7 Correction to Section number reference7.11.2 Correction to text7.12 Additional textFig 7.27 Additional note and symbolFig 7.28 Additional note and symbolFig 7.29 Additional note and symbol, width correctionFig 7.30 Additional note and symbolFig 7.31(a) Additional note and symbolFig 7.31(b) Additional note and symbolFig 7.32(a) Modifications to diagramFig 7.32(a) Change to channel typeFig 7.32(b) Modifications to diagramFig 7.32(b) Change to channel typeReferences Additional references included


7

September 2004 7-1


7

Acknowledgement

This Chapter is based on the Roads and TrafficAuthority of NSW Road Design Guide Section 3 -Cross Section. Details of the elements in theChapter have been modified to suit Queenslandpractice and conditions, but the structure of theChapter and much of the text has been adoptedfrom the RTA Guide. The assistance of RTA indeveloping this Chapter is gratefullyacknowledged.

7.1 Introduction

7.1.1 General

The cross section of a road is a vertical plane, atright angles to the road control line, viewed in thedirection of increasing chainage, showing thevarious elements that make up the road’sstructure. A cross section can show transversedetail from boundary to boundary, detailing thevarious road components.

The aim of a cross section is to show variationswithin the design and its interaction with thenatural topography. A design should besympathetic to the natural environment and userexpectations, while maintaining a balancebetween construction, maintenance and operating(including accident) costs.

The major elements of a road cross section areillustrated in Figure 7.1. More extensive detailsare shown in Section 7.11.

Three factors are fundamental to the use of thissection of the Road Planning and Design Manual:

The Total Package

The elements comprising a cross section form partof a package; accordingly, decisions about thedimensions to be adopted for an individualelement must recognise the considerable degreeof inter-dependence of design considerations that

occurs. For instance, decisions on shoulder widthcan only logically be made in the light of theavailable sight distance due to vertical andhorizontal alignments, the pavement surfacetreatment, adjoining travel lane widths andpredicted traffic volumes and composition. (Seealso Chapter 10 for coordination with alignmentdesign). A holistic approach has to be taken to thedesign and the cross section has to be designed inconjunction with the landscape elements (referRoad Landscape Manual, Main Roads 1998).

Relative Costs

For most works the cost of providing thepavement, and its wearing surface, is the mostsignificant factor in the total cost of a road project.It is therefore important to ensure that the width ofpavement adopted is the appropriate one for thecircumstances. Because pavement materials areexpensive, small increases in the width of lanesand shoulders can add significantly to the totalcost of the project, even if the percentage increaseis relatively small.

Particular care is needed in cases whereimprovements are being made to roads on theexisting formation. Adopting dimensions that willrequire widening of the formation will cause alarge increase in the cost of the work. However,once established on a project, marginal increasesin dimensions may not represent a significantincrease in the total cost.

Designers should examine the cost of alternativesto ensure that the most cost effective solution isadopted.

Clear Zones

Vehicles run off the road; hence shoulder, vergeand batter design must make provision for a clearzone (see Figure 7.1) which will allow an errantvehicle to traverse this area, sustaining minimumdamage to itself and occupants (see also Sections7.5 and 7.6).

Chapter 7Cross Section

7-2 September 2004

The clear zone concept underlines the fact that areasonably flat, well compacted and unobstructedroad side environment is highly desirable,especially on high travel speed roads.

Urban areas have specific problems created byutility poles. However, efforts should still bemade to ensure that the appropriate speed relatedclear zone is provided, especially on newconstruction. In urban areas, footpaths willprovide an adequate clear zone, provided utilitypoles, sign supports and heavy structures are keptto the rear of the footway, or made frangible, andall planting consists of frangible species.Undergrounding of Public Utility Plant will assistin keeping the footpath clear.

Figure 7.1 Typical Clear Zone

7.1.2 Cross SectionDetermination

The Flow Chart given as Figure 7.2 details theprocedure to undertake in determining the mostappropriate cross section to be adopted.References to other sections of the Road Planningand Design Manual are given for assistance.

7.1.3 Terminology

A.A.D.T.Total yearly traffic volume in both directions,divided by the number of days in the year givesthe Annual Average Daily Traffic volume.

Auxiliary LaneA portion of carriageway adjoining throughtraffic lanes, used to separate either fasterovertaking traffic or slower moving vehiclesfrom through traffic, or for other purposessupplementary to through traffic movement.

BatterThis is the uniform side slope of a cutting or anembankment, expressed as a ratio of 1 unitvertical on X units horizontal.

Batter DrainA lined open drain for removing stormwaterfrom the top to the toe of the batter in order toreduce scour of the batter face.

Batter RoundingCurvature that is applied to improve thestability and appearance of the road at theintersection of the extension of the roadcrossfall and/or existing surface (hinge point),with the batter slope of an embankment orcutting.

BenchThis is a ledge that is constructed on a batter ornatural slope for the purpose of providingadequate horizontal sight distance, greatersecurity against batter slippage or to assist withbatter drainage.

Batter Verge Shoulder Lane

Travelled WayClear Zone

Embankment

Batter Verge Shoulder Lane


Cutting

Footway Lanes


Urban Areas

*

* Width of Channel


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September 2004 7-3


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Is the project on a National-Highway?

Does this satisfy minimum lane width values?

Determine appropriate shoulder widths. See 7.3

Are batter slopes flatter

than 1 on 3 possible?

What is the appropriate clear zone

according to design speed and batter

configuration. See 7.6

Apply rounding for traversable or

recoverable batter slopes See 7.8.3

Determine appropriate treatment for ALL

hazards within the clear zone.

See Chapter 8 - Safety Barriers and

Roadside Furniture

Consider safety barrier

installation.

Does the adjusted construction

width still fit within road reserve?

Can the batter slope/s be adjusted to fit

construction width within the road reserve

considering all requirements

Is additional width required

behind the barrier or terminal

to accommodate deflection?

Adjust the formation width to

accommodate deflection of

the proposed barrier

Consider warrants for Lay bys, emergency

phone bays, bus stops, inspection bays etc.

Determine the minimum lane widening

required.

See Chapter 11 - Horizontal Alignment.

Determine the minimum lane widening

required. See Chapter II- Horizontal Alignment.

Ascertain the

lane width.

minimum

See 7.2

Ascertain number of lanes and widths

required for the predicted design traffic volume

Calculate the effective

lane width. See 7.2

Is the formation width known?(Median + lanes + shoulders + verges)

Consider warrants for Auxiliary lanes, Medians, Separated carriageways, Cycleways, etc.

Adopt National

Highway standards

for lane and shoulder

widths

See 7.2.5. And 7.3.7Collect Data: Traffic volumes, Traffic composition,

proposed speed zone, max. grade,

horizontal alignment, accident history, etc.

YES

YES

YES

YES

YES

YES

NO

NO

NO

NO

NO

Determine batter slopes according to Geotechnical data, stabilisation treatment,

maintenance, environmental and aestetic values

Adjust the cross section elements to

accommodate the required

stabilisation, landscaping, drainage

environmental treatments

YES

NO

Prepare plans for the acquisition

of additional land

NO

Figure 7.2 Cross Section Determination

7-4 September 2004

BermA ledge formed at the bottom of an earth slopeor at some level intermediate between thebottom and the top.

CapacityThe maximum rate of flow at which vehiclescan traverse a point or segment of a lane orroadway during a specified time underprevailing roadway and traffic conditions,expressed as vehicles per hour.

CarriagewayThat portion of the road formation, includinglanes, auxiliary lanes and shoulders that is setaside for the use of vehicles, either moving orstationary.

Catch BankA small catch levee constructed along the highside of a cutting to intercept and direct the flowof surface water.

Catch DrainA surface channel constructed along the highside of a road or embankment outside the batterto intercept surface water.

Clear ZoneThis is the border area that begins at the edge ofeach travelled lane and is available foremergency use by errant vehicles who run offthe road. This zone includes any adjoininglane/s, road shoulder, verge and batter.

CrossfallExpressed as a percentage, this is the crossslope of the road surface at right angles to theroad alignment. (Applied for pavementdrainage.)

Cross SectionA vertical view made at right angles to thecontrol line, showing the natural ground andthe various elements that make up the road’sstructure.

Curve WideningWidening is applied, additional to the normallane width on some curves. This additionalwidth caters for widths of the turning vehicle

due to tracking, steering inaccuracies andvehicle slippage.

CyclewayA separate path or a portion of the road (eithershared or exclusive) allotted to the use ofcyclists.

Declared RoadAny road in the State of Queensland declared tobe a road under the control of the state underthe Transport Infrastructure Act 1994.

Design SpeedA nominal speed adopted for the design of thegeometric features of the road.

DykeA low embankment of earth, asphalt orconcrete placed near the edge of embankmentsto control water movement.

Effective Lane WidthThis is the dimension of a lane that is measuredfrom the centre of a lane line to the centre of alane line or from the centre of a lane line to theface of the kerb.

FootpathThis area is located between the face of thekerb and the property boundary for use bypedestrian traffic, possible bicycle traffic andalso for the placement of utility services.

FootwayA pedestrian facility on a bridge.

Hinge PointThe point where the extended crossfall of theverge area meets with the batter slope. Thispoint is associated with rounding where it isapplied.

LanePart of the roadway set aside for the normalmovement of a single stream of vehicles.

Lay BysLay bys are short lengths of widened, sealedshoulder that is provided for the purpose ofvehicles to stand clear of the carriageway.


7

MedianThe central strip of road not intended for use bytraffic, which separates opposing traffic flows.Median width includes both adjacent shoulders.

Median Cross-overA sealed section of roadway that is providedbetween separated carriageways for thepurpose of allowing cross-median movements(often for emergency vehicles).

National HighwayHigh speed route linking the Nation’s Statecapital cities and major provincial centres, asdetailed under the National Highway Act of1986.

NearsideThis is the left hand or kerb side of a vehicle,relative to the direction of travel.

OffsideThis is the right hand or median side of avehicle, relative to the direction of travel.

Outer SeparatorThis is the portion of road reserve that separatesa through carriageway from a service orfrontage road.

Parking LaneLane primarily used for vehicle parking.

Service RoadA subsidiary carriageway that is constructedbetween the principal carriageway and theproperty line, and connected only at selectedpoints with the principal carriageway.

ShoulderA shoulder is that portion of the carriageway,measured from the outside edge of the outertraffic lane, adjacent to and flush with thesurface of the traffic lane. The shoulderexcludes any berm, verge, rounding or extrawidth that is provided for the installation ofsign posts, guide posts or safety barriers.

Shy LineThis is the offset to a hazard that a driverperceives to be adequate for his current travelspeed adjacent to that hazard.

Split Level CarriagewaysTwo similarly aligned, separated, andindependently graded carriageways.

SuperelevationThe continuous transverse slope normallygiven to the carriageway at horizontal curves.

Table DrainThe drain (lined or unlined) that is locatedadjacent to the shoulder of the road in cutting,usually having an invert lower than the sub-grade level, and formed as part of theformation.

TerrainThe shape of the natural landscape surroundinga road, broadly classified as follows-• Easy relatively level terrain, large horizontal

radii joined by long straights with cuttingsand embankments on average 2m high, withroad grades up to 2.5%.

• Average rolling terrain, with cuttings andembankments that are on average 5m high,with road grades up to 5%.

• Difficult mountainous terrain, minimumhorizontal radii, where climbing lanes maybe required, with cuttings and embankmentsgreater than 10m high and road gradessteeper than 5%.

Travelled WayThe portion of the carriageway that is assignedto moving traffic, excluding shoulders andparking lanes.

Traversable BatterA batter offering errant vehicles safe travelduring a run-off-the-road incident, bringing thevehicle to rest in an upright position.

Turning LaneAn auxiliary lane reserved for turning traffic.

VergeThe area located between the outer edge of theshoulder and the batter hinge point, used for thepurpose of providing drainage, safety barriersand rounding.

September 2004 7-5


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7-6 September 2004

7.2 Lanes

7.2.1 General

The traffic lane is that part of the roadway setaside for the normal one way movement of asingle stream of vehicles.

Traffic lanes carry out a variety of functionsimportant to the overall efficient function of theroad hierarchy:

• through road;

• rural or urban;

• special - bus, transit etc.;

• auxiliary (turning or overtaking);

• parking;

• cycleways.

Both the lane width and the road surface conditionhave a substantial influence on the safety andcomfort of users of the roadway. In ruralapplications, the additional costs that will beincurred in providing wider lanes, will be partiallyoffset by the reduction in long term shouldermaintenance costs. Narrow lanes result in agreater number of wheel concentrations in thevicinity of the pavement edge and will also forcevehicles to travel laterally closer to one anotherthan would normally happen at that design speed.

Drivers tend to reduce their travel speed, or shiftcloser to the lane/road centre (or both) when thereis a perception that a fixed hazardous object is tooclose to the nearside or offside of the vehicle.When there is a perceived fixed hazard there is amovement by the vehicle towards the oppositelane line. The offset of this fixed hazard from theedge of the lane where this reaction starts to beobserved is called the “Shy Line”.

The shy line is taken as the distance from the edgeof travelled lane to the outer edge of shoulder,provided that there is a significant length ofconstant width shoulder in advance, or as thedistance as shown in Table 7.1, whichever is thegreater.

Table 7.1 Shy Line Distances

85th Percentile Shy Line Distance (m)Speed (km/h) Nearside Offside

(Left) (Right)≤70 1.5 1.080 2.0 1.090 2.5 1.5

≥100 3.0 2.0

Depending on the lane configuration and the roadalignment, a reduction in lane width/s reduces thelateral clearance between vehicles leading toreduced travel speed and lane capacity. Tables 7.2and 7.3 show lane capacity reductions accordingto clearances from lateral fixed hazards.

Table 7.2 Two Lane Roadway

Lane CapacityClearance (% capacity of 3.5m lane)

3.5m 3.3m 3.0m 2.7mlane lane lane lane

1.8 100 93 84 701.2 92 85 77 650.6 81 75 68 570.0 70 65 58 49

Table 7.3 Four Lane Undivided Roadway

Lane CapacityClearance (% capacity of 3.5m lane)

3.5m 3.3m 3.0m 2.7mlane lane lane lane

1.8 100 95 89 771.2 98 94 88 760.6 95 92 86 750.0 88 85 80 70

The widths of all lanes adjacent to kerblinesexclude the width of the channel.

It must be remembered that the legal width limitof commercial vehicles is 2.5m. The majority ofheavy vehicles are built to this maximum width,BUT it does not include the additional 200 mmwidth on each side of the vehicle generated bywing mirrors.


7

ARRB Transport Research was commissioned todevelop minimum estimated lane widthrequirements for various heavy vehicles. Datafrom this study is presented in the histogram“Minimum Estimated Vehicle Path” (Figure7.2.1).

This figure does not include a clearancecomponent. Typically an additional 0.5m is addedto the given widths to determine the lane width.

These minimum vehicle path width values arebased on straight travel, a road roughness of 120counts/km (NAASRA), average crossfall of 4.5%and two test speeds. This particular combinationwould be regarded as too extreme for typicalsituations, but no other data is available at present.Furthermore, a different set of test conditionswould need to be considered for roads withgeometry other than straight paths.

The research suggests that most vehicles, with theexception of Type 2 road trains or rigid truck plus3 trailers, could comfortably operate along roadsthat have a usable lane width of 3.5m, in a speedenvironment of 90km/h. The operating speed forType 2 road trains is 80km/h, therefore somereduction of road width requirement from thosegiven could be expected. Generally, pastperformance suggests that Type 2 road trains canoperate adequately in 3.5m lanes with 1m sealedshoulders on straights with 3% crossfall.

7.2.2 Two Lane Two Way RuralRoads

Minimum traffic lane widths for two lane two wayrural road applications should be determined fromTable 7.4.

Where the intended design speed throughmountainous terrain will be in excess of 80 km/h,or 100 km/h in undulating terrain, or where thereis a predominantly high percentage of heavyvehicles (20% for 500 AADT and 5% for 2000AADT), a lane width of 3.5 m is desirable.

Refer to Section 7.2.1 for discussion on variousheavy vehicles.

Table 7.4 Guidelines for Traffic Lane Width (TwoLane Rural Roads)

Width of Anticipated AADT at OpeningTraffic Low Reasonable HighLanes Future Future Future

Growth Growth Growth(<3)% (3-6)% (>6)%

Two Lanes (6.0) up to 700 up to 500 up to 300(6.5) 700-1700 500-1200 300-900(7.0)* over 1700 over 1200 over 900

* Where local conditions dictate, widths in excess of7.0m may be considered.

If in using the table, volumes fall near the boundary ofgroups, consider carefully whether to use higher orlower value.

September 2004 7-7


7

Prime Mover/Semi Trailer (19m)

Truck/Trailer (R12T12)

Truck/Trailer (R12T22)

A-Double (Type1 road train)

A-Triple (Type 2 road train)

19m B-double

25m B-double

B-Triple

Rigid +3 (Not Permitted in Qld)

0 0.5 1 1.5 2 2.5 3 3.5 4

60kmh

90kmh

Widths (m)

60km/h

90km/h

Figure 7.2.1 Minimum Estimated Vehicle Path

7-8 September 2004

7.2.3 Multilane Rural Roads andMotorways

The lane widths provided on multilane rural roadsshould be 3.5m. Desirably any rural roadconsisting of four lanes or more should have acentral median, separating opposing traffic flows.

The normal lane width on Motorways is 3.5m.Where a one-way carriageway is three lanes ormore, the central lane/s should be 3.7m (seeFigure 7.32).

7.2.4 Urban Roads

It is desirable for traffic lanes on urban roads to be3.5 m wide but if the road reserve is restricted oran on-road bicycle lane is required, the lanewidth/s may be reduced.

Quite often the designer is faced with the task of“squeezing” an extra lane or bike lane from anexisting or partially widened road formation. Ithas been observed in the Netherlands that wherebicycles are mixed with general traffic, eithernarrow (3.0 to 3.3m) or wide (3.7 to 4.0m) lanesshould be used. Intermediate widths (3.5m) tendto be wide enough to encourage cars to passbicycles, but not wide enough to do so safely.Where bicycles are to be accommodated in thekerb lane, the wider lanes are preferred.

To allocate lane widths on an equitable basis, thediffering functions and interfaces of each laneneeds to be taken into account.

It should be noted that “effective” lane widths aremeasured from the centreline of linemarking orfrom the face of the kerb. See Figure 7.3.

The restrictions encountered will often requirelane widths to be reduced to fit the requirednumber of lanes into the available space. Thesewidths can be as low as 3.0m and can vary up tothe desired width of 3.5m. The minimum lanewidths to be adopted are as follows:

• Straight 3.1m for kerbside lanes; 3.0mAlignment for other lanes

• Curved widening in accordance with Alignment Table 11.8 of “Chapter 11:

Horizontal Alignment” shouldbe applied.

Where lanes are adjacent to barrier kerbs, it isdesirable to locate the kerb at least 0.5m from theedge of the lane to compensate for the tendency ofthe driver to shy away from the kerb. Usually, thewidth of the channel is satisfactory for thispurpose.

For routes accommodating multicombinationvehicles (MCV), allowance has to be made for thesize of vehicles and their tracking characteristics.Appendix B sets out the minimum requirementsfor these routes.

Figure 7.3 Lane Width Notation

7.2.5 National Highways

National Highway design should provide aconsistent design form, enhancing a high speedenvironment in an aesthetically pleasingsurrounding. The width of all lanes shall be notless than 3.5m.

7.2.6 Bus Routes

• New construction on roads with bus routesshould provide for a desirable kerb lane widthof 3.7m and a minimum of 3.3m except wherethe bus route forms part of the cycle network inwhich case the minimum kerb lane width willbe 4.1m. It may be necessary to take width offother traffic lanes to allow for this.Alternatively, a suitable bicycle route can bededicated in the same corridor. (Note that busesin Brisbane City occupy 3.15m when mirrors


7

are included.)

• On existing roads with bus routes the followingconditions apply:

1. Kerbside lanes to be marked not less than3.0m width, from the face of the kerb.Where the lane widths are 3.0 m or less, thekerbside lane should be marked wider thanthe adjacent lanes to offset the effects ofkerbs, channels, power poles and otherroadside structures.

2. Site specific measures to mitigate the effectof the narrow lane should be investigated.These include parking restrictions, medianadjustments, indented bus bays and so on.

3. Discussions should be held with theappropriate Queensland Transport Manageror private bus operator during the planningstage to ensure that arrangements areacceptable.

(See “Guide to Traffic Engineering Practice - Part11, Parking” (Austroads, 1995b), for bus bays.)

7.2.7 Auxiliary Lanes

For auxiliary lanes other than parking and turninglanes, the lane width should be the same as theadjoining lanes (see Chapter 15, Auxiliary Lanes).

Auxiliary Lanes located on steep grades are to beprovided on the offside where analysis shows thatthey will be cost effective. (See Chapter 15.)

The configuration will require drivers ofovertaking vehicles to move to the right, out of thenearside lane. Overtaking vehicles will move tothe offside lane, returning to the nearside laneafter completing the overtaking manoeuvre. Anemergency runoff (sealed hard stand at least 3.0 mwide) is to be provided on the nearside at the endof the merge (see Figure 15.6, Chapter 15).

On some grades, short passing bays aresometimes placed on the nearside of the throughlane to allow slow vehicles to pull over. The widthis to be the same as the adjacent lane. (SeeChapter 15 for details.)

7.2.8 Parking Lanes

Parking Lanes adjacent to urban roads are normalpractice. In rural situations, parking lanes are notprovided but some provision for parking at reststops and motorist stopping places may be made -see Chapter 20 for these cases.

In urban roads, the parking lane often fulfils thefunction of a shoulder as discussed in Section 7.3but its use is predicated on traffic and servicegrounds exclusively. It is useful to consider thefunctions of various types of urban roads to put thedecision on the cross section required in context.

Major Routes - Single Purpose

These comprise the through pavements of limitedaccess routes and urban motorways. The roadcaters for moving traffic and occasional stops andthe design parameters are similar to those of ruralroads. Traffic lanes and shoulders are providedand rural forms of cross section are acceptable.Parking is not an issue other than providing forstopped vehicles (broken down, fatigue etc.).

Major Routes - Mixed Purpose

These form the bulk of major urban traffic routes.They carry frontage development and hence caterfor access movements, parked vehicles andparking and unparking of those vehicles as well asfor moving traffic. Design principles differ fromthose of rural roads. Cross sections include trafficlanes, bicycle lanes and parking lanes (oftenserving the function of shoulders).

Local Access Roads

The principal design factors relate to propertyaccess, property drainage and width betweenkerbs. Providing for parked vehicles within thecross section is important.

Frontage/Service Roads

These roads are not a separate class but may beeither local access or mixed purpose roads. Thelowest class of service road provides only forlocal access (residential access, industrialdevelopment, and shopping centres). On majorurban corridors in large cities, they can eventually

September 2004 7-9


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7-10 September 2004

carry significant proportions of traffic other thanfor local access purposes.

As the through significance of the main pavementof the service road increases, there is a tendencyfor fewer connections to the rest of the streetsystem. In these cases, the service roads tend to amixed function status with increasing importancegiven to other than local accessing traffic. Theycan ultimately become arterial/collector roads intheir own right.

Widths

An exclusive parallel parking lane should be aminimum of 2.5m wide. If a kerb and channel isprovided on the road, the width of the channelmay be used as part of this minimum widthalthough this is undesirable. This minimum widthshould only be used in situations where there is nolikelihood of the lane being required for trafficpurposes in the future and the reduced capacity ofthe road produced by this arrangement is adequatefor the traffic volumes expected.

A parallel parking lane used as a travel lane duringpeak times, should be the same width as normalurban travel lanes, namely a desirable width of 3.5m and a minimum of 3.0 m to the lip at thechannel. Where bicycles are to use the kerb lane,the desirable minimum width is 3.7m, but a widthof 3.5m should be avoided (see 7.2.4).

Shared parallel parking and traffic lanes should be5.5m wide (3.5 travel lane + 2.0 parking lane tothe channel lip) and an additional 1.0 - 1.5mwhere there is a shared bicycle and parking lane.(Refer to Austroads, 1995b and Chapter 5.) This isthe borderline between acceptable and difficultoperation.

In areas where frequent parking is combined withreasonable arterial volumes there is merit inputting all spare width into the outer lane/parking

lane combination as this is where most of the“frictions” occur. This applies principally tosuburban shopping/business areas on arterialroads. In these cases, as speeds tend to be slowedthere is merit in reducing through lane widths andusing minimum median width betweenintersections to obtain this additional space.

Where angle parking is adopted, the width andmarkings defined in the Manual of UniformTraffic Control Devices should be adopted.

Parking restrictions at intersections

Parking should be designed so as not to interferewith sight distance or impede the flow of trafficturning at an intersection. Regulations prohibitparking within certain distances from the crossroad property boundaries.

Table 7.5 indicates the distances over whichparking is prohibited at an intersection. Distancesgiven are for both signalised and non-signalisedintersections.

7.2.9 Turning Lanes/TurningRoadways and Ramps

The desirable width for turning lanes is 3.2 - 3.5mwith a minimum width of 3.0m. The width of rightturn storage lanes should be determined inconjunction with median widths. See Chapter 13,Intersections at Grade.

One lane ramps at the interchanges are generally4.0m wide. If two or more lanes are required, thewidth of the lanes is to be 3.5m (see Chapter 16).


7

Non-signalised Intersections Signalised - Major Roads Signalised - Other

Approach Depart Approach Depart Approach DepartParallel Parking 6.0 m 6.0 m

100.0 m 100.0 m 30.0 m 15.0 mAngle Parking 12.0 m 9.0 m

Table 7.5 Distances over which Parking is Prohibited at an Intersection

7.2.10 Cycleways

Where bicycle lanes are provided on routes,appropriate widths for shared and exclusivebicycle lanes are given in Chapter 5, which havebeen derived from “Guide to Traffic EngineeringPractice, Part 14 - Bicycles” (Austroads, 1999).See Table 7.6. Exclusive lanes are preferred wherespace is available.

Table 7.6 On Road Bicycle Lane Widths

Speed Facility Lane Width(km/h) (m)

60 Exclusive lane 1.580 Exclusive lane 2.0

100 Exclusive lane 2.560 Shared with parking lane 4.0*80 Shared with parking lane 4.5

* 4.5m preferred to allow cyclists to avoid openingdoors on parked cars.

Figure 7.4 shows the lateral forces which areapplied to cyclists when in close proximity toheavy vehicles travelling at speed.

Lane widths that may result in a squeeze point forcyclists should be avoided if possible. On lefthand curves, parked cars tend to “truncate” thecorner and use up space allocated to cycles in ashared lane. Restriction of parking in thesecircumstances should be considered.

Cyclists have a legitimate claim to use publicroads and provision is to be made for them. Theycan be on or off the carriageway (i.e. elsewherewithin the road reserve or on a separate route). Onmotorways, cycleways must be separate from thecarriageway as required by the motorwaylegislation.

Elements constructed on the path provided forcyclists are to be designed on the basis thatbicycles will have tyres that are a minimum of 20mm wide (e.g. bicycle safe grates).

September 2004 7-11


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Note: Lateral forces may be increased where enclosed roadways (e.g. under bridges) create a “wind tunnel” effect.In these cases, it may be appropriate to encourage cyclists to use the footpath (fencing, signage) to increase theseparation distance.

Figure 7.4 Lateral Forces on Cyclists, Induced by Heavy Vehicles

7-12 September 2004

Adjoining furniture is to be free from protrusionsthat may snag the clothing of cyclists, or causeunnecessary injury in a fall.

Where a safety barrier is erected and there is awarrant to provide additional protection toprevent cyclists suffering injuries from fallingover the top of the barrier (such as on bridges withdrops of more than five metres), a 75 mm (min.)diameter rail 1400 mm high is to be provided ontop of the concrete barrier. The rail must not havepotential to spear an impacting vehicle. It is notrequired where the height of the safety barrier is1200 mm or higher.

Where the cycleway is adjacent to guardrail inthese conditions, a weld mesh fence 1400mm highshould be placed behind the guardrail.

7.2.11 Location of Kerb and/orChannels

In general, kerbs should be avoided in high speedenvironments. Where they are used, kerb and/orkerb and channel are located outside the travellanes on both the nearside and offside of the road.A 1.0m offset to the kerb face shall be providedwhen the design speed is > 80km/h. If the designspeed is < 80km/h, an offset of 0.5m is permittedin unlit situations with 0.0 m offset permitted in litareas. (See Section 7.4.5).

7.2.12 Transit Lanes

Transit lanes are discussed in some detail inChapter 2. This Chapter deals with the physicallayout of various treatments and appropriatedimensions for components.

Design Principles

• Transit lanes should be accompanied byindented bus bays, so through traffic (includingexpress buses) and emergency vehicles canavoid being trapped behind a stopped bus;

• Signal phasing needs to be designed to ensurethat bus drivers do not avoid bus queue jumplanes (advance green light for buses) in favourof using the general purpose lanes;

• Bus stops should be placed on the moreefficient far side or mid-block locations;

• Designs must accommodate left-turninggeneral purpose vehicles without impeding theflow of through High Occupancy Vehicles(HOVs);

• Queue jumps must be sufficiently long to bepractical and must be effectively signed;

• Priority lane signage and pavement markingshould be substantially enhanced and designedfor high impact;

• Design should support enforcement and mustbe developed in consultation with the Police;

• The needs of bicyclists should be fullyaddressed and the synergies between the often-overlapping priority rules for cycling andHOVs should be captured; and

• Transit lanes should be implemented within thecontext of a network strategy or framework toensure that they contribute to a treatment longenough to create sufficient time savings toinduce modal shift and encourage car-pooling.

Alternative Treatments

Providing priority treatment for HOVs is not anew concept, nor does it necessarily involveradical or unconventional changes to the streetsystem. It can be as simple as putting up somesigns designating a certain lane for bus use onlyduring specified hours.

For each case, alternatives are grouped in threecategories:

• segment treatments;

• intersection treatments; and

• spot treatments.

There is some overlap, and a single corridor couldconceivably use several different treatments overits length, but each alternative can be identifiedand illustrated as a stand-alone option at thisstage. The “do nothing” and “improve general-purpose traffic” options also need to be includedwhen assessing alternatives at the corridor level.


7

The alternatives are listed below, and areillustrated in Figures 7.2.12.1 to 7.2.12.4. (Nodistinction is made between use as a T2, T3, orBus Facility.) The issue of widening versus laneconversion is also not addressed here; it will needto be considered at the individual corridor level.Similarly, care must be taken to distinguishbetween the priority treatment type and the roadtype - a kerbside bus lane has the samecharacteristics no matter what type of road it is onor how the general-purpose lanes are treated.(Reference: PPK, 2000).

Group A: Segment Treatments

A-1: Kerb Lane

A-2: Second Lane

A-3: Median Lane

A-4: Contraflow Kerb Lane

A-5: Contraflow Median Lane

A-6: Single Reversible Median Lane

A-7: Two Way Median Lanes

All of these alternatives are illustrated in Figure7.2.12.1.

Group B: Intersection Treatments

B-1: Signal Priority Figure 7.2.12.2

B-2: Queue Jump Lane Figure 7.2.12.2

B-3: Advance Signal Figure 7.2.12.2

B-4: HOV Turn Lane Figure 7.2.12.3

B-5: HOV Grade Separation Figure 7.2.12.3

Group C: Spot Treatments

C-1: Ramp Meter Bypass Lane Figure 7.2.12.4

C-2: Priority Link Figure 7.2.12.4

C-3: Exclusive Ramp Figure 7.2.12.4

The dimensions of the lanes, medians andseparators required for these alternatives shouldcomply in principle with the requirements of this

chapter. Some compromise may sometimes berequired to accommodate the limited spaceavailable on an urban road - the allowable rangeof dimensions is provided in the relevant parts ofthis chapter. Typical dimensions of componentsare shown in the typical cross sections in Figures7.2.12.5 to 7.2.12.10.

Chapter 5 provides details of the turningrequirements for buses and trucks, and discussesthe needs of bicycles.

Access

Ingress to and egress from buffer and barrierseparated Transit lanes should occur atstrategically located openings located sufficientlyupstream and downstream of interchange rampsto allow adequate weaving. Typical weaving zonelength is 400m located 150m per lane-changefrom the ramp (see Figure 7.2.12.11).

For further details on access requirements, refer toWilden (1997).

Enforcement

Enforcement of the correct use of transit lanes isrequired and adequate space to allow safeenforcement activity has to be provided.

This can be achieved by using a continuous 3.5mwide shoulder. This width is required to providespace for the enforcement activity - a lesser widthwill not be usable. Figures 7.2.12.5 to 7.2.12.8show typical arrangements for enforcement areas.

It may be possible to reduce the cost of acontinuous 3.5m shoulder by providingintermittent enforcement bays 100m long withappropriate deceleration and acceleration lanesand tapers at each end. The length of thedeceleration lane should be based on being able tostop at the start of the bay; the length of theacceleration lane should be based on a start speedof zero at the end of the bay.

September 2004 7-13


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7-14 September 2004


7

TL

BU

SS

TO

P

TL

A1: Typical Arrangement,Kerb Lane HOV Facility

A2: Typical Arrangement,Second Lane HOV Facility

TL

ONE WAY TWO WAY

OR

TL TL

A3: Typical Arrangement,Median Lane HOV Facility

TL

A4: Typical Arrangement,Contraflow Kerb Lane HOV Facility

TL

A5: Typical Arrangement,Contraflow Median Lane HOV Facility

A6: Typical Arrangement,Single Reversible Median Lane HOV Facility

TL

BU

SS

TO

P

TL

AM

PM

A7: Typical Arrangement,Two Way Median Lanes HOV Facility

Figure 7.2.12.1

September 2004 7-15


7

TL

B2: Typical Arrangement,Queue Jump Lane

B1: Typical Arrangement,Signal Priority

BU

S

VehicularDetectionSystem

TrafficSignal

Controller

TEE Intersection

TLOR

TL

B3: Typical Arrangement,Advance Signal

Right Turn from Kerb Lane Bottleneck

TL

Figure 7.2.12.2

7-16 September 2004


7

B4: Typical Arrangement,HOV Turn Lane

B5: Typical Arrangement,HOV Grade Separation

TL

TL

OR

TL

TL

TL

TL

TL

TL

TL

Figure 7.2.12.3

September 2004 7-17


7

C1: Typical Arrangement,Ramp Meter Bypass Lane

C2: Typical Arrangement,Priority Link

C2: Typical Arrangement,Exclusive Ramp

TL

TL

TL

TL

TL

Figure 7.2.12.4

7-18 September 2004


7

general purpose

lane

1.2m 3.5m 3.5m

reversible lane(s)

CL

general purpose

lane

1.2m

HOV LANE HOV LANE

SHOULDER SHOULDER

3.5m

Figure 7.2.12.5 Barrier Separated Reversible Cross Section

general purpose

lane

1.2m 3.5m

HOV LANE

3.5m

SHOULDER

1.2m

general purpose

lane

1.2m3.5m

HOV LANE

3.5m

1.2m

Figure 7.2.12.6 Barrier Separated Two-Way Cross Section

3.0m

HOV LANE

SHOULDER

general purpose

lane

3.5m 3.5m

HOV LANE

3.0mgeneral purpose

lane

3.5m3.5m

SHOULDER

Figure 7.2.12.7 Concurrent Flow - Non-Separated HOV Lanes Cross Section

3.0m

HOV LANE

SHOULDER

general purpose

lane

3.5m 3.5m

HOV LANE

3.0mgeneral purpose

lane

3.5m3.5m

SHOULDERBUFFERBUFFER

1.2m 1.2m

Figure 7.2.12.8 Concurrent Flow - Buffer Separated HOV Lanes Cross Section

SHOULDER

general purpose lane

SHOULDERBUFFERBUFFER

PEAK DIRECTIONTRAFFIC FLOW MOVABLE BARRIER

HOV LANE

general purposelane

OPPOSINGTRAFFIC FLOW

Figure 7.2.12.9 Typical Contraflow Lane Configuration Cross Section

September 2004 7-19


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General Purpose Lanes

RAMP METERING AND HOV BYPASS LANE

General Purpose Lanes

Enforcement Area

High-occupancy Vehicle Bypass LaneRamp Meter Signal

SEPARATED QUEUE BYPASSLocal Street

Figure 7.2.12.10 Queue Bypass (See also Chapter 16, Figure 16.8)

150m

Barrier

Start of Buffer150m

Exit Entry

150m

150m

Ingress Distance ata minimum of 150m

per lane change

Egress Distance ata minimum of 150m

per lane change

150m

150m

150m

Figure 7.2.12.11 Ingress and Egress Weave Distance at Buffer Separated Facilities

7-20 September 2004

7.3 Shoulders

7.3.1 General

The shoulder is that portion of the carriagewaybeyond the traffic lanes, adjacent to, and flushwith the surface of the pavement. Its purpose is toaccommodate stopped vehicles, provide lateralsupport to the road pavement layers and, if sealed,offer improved conditions for cyclists.

The shoulder width is measured from the edge ofthe traffic lane to the verge. All safety barriers,signs, guide posts, drains and kerbs are to becontained outside the shoulder within the verge.Fixed objects within the verge should be frangibleor protected with a safety barrier (see Section 7.5,Verges).

Factors to consider in deciding on shoulder widthinclude:

• Support for the pavement structure - 0.5m willaccomplish this;

• Space for a driver to use to avoid a collisionand regain control - the shoulder width willrarely be sufficient to accomplish this and the“clear zone” will be the area in which thisoccurs. However, the wider the shoulder, themore use it will be for this purpose - a width of3.0m would be desirable (North Americanstudies show that the accident risk is halvedwhen hard shoulder width is increased from 0.6to 3.0m - Ref. 4);

• Clearance to posts and other fixed objects toprovide an adequate distance to the shy line(see Table 7.1) - (this will also allow marginalincreases in the numbers of vehicles carried ata particular level of service but this effectdisappears over widths in excess of 1.5m);

• Space for a stationary vehicle to stand clear orpartly clear of the traffic lanes - 2.5m isrequired for a passenger vehicle to be clear ofthe traffic lanes and greater widths provide foradditional clearance or for larger vehicles tostand clear;

• Provision of a bicycle lane (see Chapter 5 andFigure 7.5);

• Sight distance across the inside of a horizontalcurve; and

• Costs of the additional width, particularlywhere the existing formation is being used - aCost Benefit analysis should be made.

7.3.2 Two Lane Two Way RuralRoads

Widths

Table 7.7 lists shoulder width requirements fortwo lane rural roads with minimal pedestrianand/or bicycle traffic.

A taper of 1:50 should be applied betweendifferent width shoulders that adjoin one another.This taper transition may need to be lengthened toensure the taper’s appearance is satisfactory.

Table 7.7 Guidelines for Shoulder Widths

Nominal SituationShoulderWidth (m)0.5-1.0* Normally widths less than 1.0 m will be used

only where overlaying is being carried outwith full formation sealing, and widening offormation is not justified.

1.0* Minimum shoulder width for general use(i.e. unless special reasons dictateotherwise). Appropriate also when shoulderseal is desired and material cost/propertiesdictate full normal paving material.

1.5* Normal shoulder width with sealed or partlysealed shoulders. Depends on availability ofsuitable material.

2.0-2.5* Suitable shoulder width on higher volumeroads when periodic provision to stopcompletely clear of traffic lanes is difficult toprovide.

3.0* Special cases where local issues dictate(e.g. high speed high volume rural routeswhere incidence of stopped vehicles unableto exercise choice as to location of stop maybe significant). Normally only occurs onarterial outlets to major urban areas,especially if recreational routes.

* Shoulders between 0.5 m and 1.5 m do not enable avehicle to stop clear of traffic lanes. 2.0 m shouldersenable it to stop largely clear. A vehicle travelling 100km would expect to encounter some 4 to 5 stoppedvehicles for every 1000 vehicles/hour using the road.Of these something less than 5% would have little


7

choice as to the exact location of the stop. There isevidence that safety does not improve significantly forshoulder widths over 1.5-2.0 m. Continuous 2.5 mshoulder can therefore be justified only on the highestvolume roads and where speeds are also high. Whatis important, however, is to provide frequentopportunities to stop completely clear of the road (byflattening slopes on at least some low fills, or makingprovision at the transition of cut and fill) on all roadswith shoulders less than 1.5 m, and also on highervolume roads with shoulders less than 2.5 m.

Shoulder Sealing

Shoulders should be sealed to a width of 0.5m(min.) from the edge of the sealed lane when thepredicted AADT is less than 2000, and 1.0m(min.) when the predicted AADT is greater than2000. When provision is made for cyclists, awider sealed shoulder is required (see Chapter 5).

A full width seal should be provided:

• Adjacent to a lined table drain, kerb or dyke;

• Where a safety barrier is provided adjacent to a1.0 m wide shoulder;

• On the outer shoulder of a superelevated curve;

• On floodways;

• Where environmental conditions require it;

• Where rigid pavement is proposed;

• Where required to minimise maintenance costs;

• In high rainfall areas.

Edge lines should be marked so that their insideedge corresponds to the outside of the lane.

Note: Sealing is sometimes continued beyond theshoulder point and down the batter slope on the highside to protect the pavement from ingress of water. Onfloodways, the seal is continued down the batter onboth sides where no other protection of the batters isprovided.

7.3.3 Multilane Rural Roads andMotorways

Rural Roads

On a rural road with a median and two lanes ormore in each direction the shoulders should be2.0-2.5 m wide on the nearside and 1.0 m wide onthe offside (median). Sealing is normally decidedon the same grounds as for rural two lane roads.

The need to provide lay bys on multilane roads isnot as critical as on two lane two way roads.However, consideration should still be given toproviding these facilities, particularly for heavyvehicles, at reasonable intervals (see Chapter 20).

Motorways

Shoulders on motorways will generally be at theupper end of the range because of the high trafficvolumes combined with high speed operation. Thedesirable minimum width of the nearside shoulder(left hand side) is 2.4m but 3.0m will be justifiedin some cases (e.g. Pacific Motorway). Theminimum width of the median shoulder is 1.0m fora two lane carriageway, and 2.0m for a three lanecarriageway. Desirably, for 3 or more lanes, a 2.4mmedian shoulder should be used to allow vehiclesto stop clear of the running lane. Note that shy linedistances to obstructions must be observed.

7.3.4 Auxiliary Lanes

Nearside shoulder widths adjacent to auxiliarylanes should generally be 1.0 m, widened to 2.0 madjacent to a safety barrier and 3.0 m at mergeareas. At merge locations it is important that theshoulder remain traffickable, thus a full width sealis desirable. (Refer Figure 15.6, chapter 15.)

7.3.5 Ramps

Desirably, minimum shoulder widths on rampsshould be 2.0 m on the nearside and 1.0 m on theoffside. Shoulder seal shall be full width. Underspecial circumstances the shoulders may bereduced but the total carriageway width shouldnot be less than 7.0 m. The range of circumstances

September 2004 7-21


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7-22 September 2004

for ramps is complex - detailed requirements aregiven in Chapter 16.

7.3.6 Urban Roads

On roads where a “traffic lanes + shoulders”design is appropriate the considerations given forrural roads apply similarly. However, urban trafficdistributions tend to be different from ruralconditions, in that urban arterial roads exhibitfrequently repeated peak hour flows. Operatingspeeds well below free running speeds arenormally associated with design volumes.Capacity is more important than speed. It is rarethat a full width, fully paved lane can beeconomically justified as a full length breakdownlane. Table 7.8 sets out guidelines for shoulderwidths for urban roads.

Table 7.8 Guidelines for Urban Shoulder Widths

Nominal SituationShoulderWidth (m)0.0 No clearance normally required between

traffic lanes and semi-mountable kerb(e.g. raised medians). An offset of 0.5 mto kerbs is desirable, and is required onNational Highways.

0.5-1.0 Normal median shoulder with depressedmedian.

1.0 Minimum outer shoulder width for generaluse (i.e. unless special reasons indicateotherwise).

1.5-2.5 Normal outer shoulder width on majorurban roads (isolated stopped vehicles on1.8 m shoulders have been shown tohave negligible effect on capacity orsafety).

3.0 Special cases where high volumes andhigh speeds can coincide, i.e. where thefrequency of stopped vehicles (highestbecause of high volumes) is associatedwith high speeds of the through traffic.This is normally associated with thearterial outlets to major cities, whererecreational peaks are much “flatter” thanurban commuter peaks, and highvolumes just below those thatconsiderably reduce speeds, can persistfor long periods.

7.3.7 National Highways

Table 7.9 gives parameters for the width ofshoulders on National Highways.

Table 7.9 Shoulder Widths for National Highways

AADT One Way Two WayLeft Right Left Right

< 3000 2.0 1.0 1.5 1.5

> 3000 2.0 1.0 2.0 2.0

7.3.8 Cycleways

Where there is an identified requirement to makeprovision for bicycle traffic, then an additionalwidth of seal may be added to the sealed shoulderwidth, which may warrant shoulder widening. SeeFigure 7.5.

Sealed shoulders have a proven road safetybenefit for all road users and reduce long termroad maintenance costs. Also, most main roadswill have some level of cycling as they providethe only connecting routes between regionalcentres. Therefore, sealed shoulders will generallybe required on all main roads with special bicyclefacilities necessary on urban main roads.

Figure 7.5 Recommended Sealed ShoulderWidths for Cyclists

Wid

tho

fS

ea

led

Sh

ou

lde

r(m

)

0.0

1.0

2.0

3.0

40 50 60

85th Percentile Speed of Trucks (km/h)

70 80 90 100 110 120


7

7.3.9 Change in Shoulder Width

Where the width of shoulder is changed for anyreason, the transition from one width to the next isto be accomplished with a taper of 1 in 50.

7.4 Medians

7.4.1 General

A median is the strip of road, that is not normallyintended for use by traffic, which separatesopposing travelled ways. The median widthincludes the adjacent shoulders (see Figures 7.30,7.31 and 7.32).

The strip of road within the median, excludingadjacent shoulders, is called a “residual median”.

Medians:

• significantly reduce the risk of collision withopposing traffic;

• improve capacity by restricting access toproperty and minor side streets;

• provide a safety refuge for pedestrians;

• prevent indiscriminate u-turn movements;

• direct right turn movements to signalisedintersections and/or right turn bays,

• provide a place to collect run-off from the roadand carry the water to the drainage system; and

• accommodate safety barriers and glarescreening.

7.4.2 Rural Roads

It is a requirement for medians to be installedwhen a rural road is widened to four lanes or moreor is constructed initially as a divided road. It isalso necessary to provide for a painted median atleast 1.0m wide in those cases where passinglanes in each direction overlap. These sectionsbecome four lane sections and it is necessary toprovide at least this degree of separation of theopposing traffic streams.

When a median is provided on a rural road, it issometimes desirable to have it in conjunction withindependently aligned and graded carriageways.Special attention needs to be given to thecarriageway relationship to alleviate the effects ofheadlight glare. Research has shown that theminimum width median to adequately separatetraffic without median barriers on high speedroads is 15 m. In cases where a variable widthmedian is provided, the width should not be lessthan the minimum widths discussed in 7.4.6.

On dual carriageways where the provision ofcross-median access for turning semi-trailers isnecessary, a wider median will be required toensure that turning vehicles are sheltered from thethrough traffic. In such cases the minimummedian width will be governed by the length ofthe design vehicle expected to utilise the facility.This may be reduced if the through carriagewaysare widened to accommodate turning vehicles(see Chapter 15, Intersections at Grade). If it isuneconomic to maintain the wide median over theentire length of the road, then local widening maybe applied.

Factors that need to be considered in reaching adecision on this include:

• What is the cost of the land required?

• Are there any other reasons why the landshould not be taken (buildings, otherdevelopments, cane land, etc)?

• How many vehicles will be using the crossing?Is the likelihood of a vehicle having toundertake a two-stage crossing high?

• A 19m median would be desirable if affordableand may allow safety barrier to be omitted; theextra width allows more flexibility in the future- the 15m is a minimum and results in a quitenarrow median in the future if widening isundertaken;

• It may be possible to provide the 19m at theintersections and use curves on each side of theintersection to transition back to the “normal”median width;

September 2004 7-23


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7-24 September 2004

• If the intersection will be signalised in the nearfuture, the width should be kept relatively smallto avoid excessive clearance times;

• A seagull intersection to accommodate the twostage right turn and maintain a lesser medianwidth may be considered (see Chapter 13);

• If the right-of-way is available, and it is a ruralarea, it is likely that the costs of providing awider median can be kept to the same, or closeto the same, cost as the narrower median. Witha wide enough median, the possibility ofindependent grading comes into play and thecosts may be reduced with smart design.

When future widening is anticipated, it isdesirable to allow for it in the median width. Theultimate median width should not then be lessthan the desirable width of 15 m.

Widening into the median will:

• Minimise traffic disruptions duringconstruction of the widening;

• Minimise interference with roadside furniture,drainage installations and environmentalprotection devices;

• Prevent further environmental damage duringconstruction of the widening; and

• Avoid disturbing cut batters (particularlyimportant in potentially unstable or erodablecountry).

There will be circumstances where widening onthe outside of the existing pavements will be theappropriate solution. These include:

• Existing ramps have to be remodelled to suitcurrent standards;

• The existing median is inadequate toaccommodate the additional lanes and retainsufficient width;

• There is little disruption to the existingdrainage and other infrastructure;

• The existing outer lane has less life remainingthan the inner lane and a new outer lane willprovide for the heavier loads allowing

additional life to be achieved for the pavementas a whole;

• The adjoining sections at the start and end of arelatively short project have to be matched.

Care is required to provide for the trafficmovements across the construction works at theaccess points.

The decision on future widening requires carefulconsideration of the factors impacting on the roadin question and adopting the solution thatprovides the best answer for the particularcircumstances.

7.4.3 Urban Roads

In urban roads it is desirable to provide medians onroads of four lanes or more. Where six lanes arerequired, medians are even more important. In thesecases, a carriageway width of >9m between kerbs isrequired to allow for at least two travel lanes plus ashared parking lane/travel lane. For carriagewaysless than 9m, parking or breakdowns will restrictflow and reduce road capacity. Medians can beprovided on roads with carriageways between 7mand 9m between kerbs if:

• mountable kerb and verge reinforcement areprovided to enable vehicles to stop clear of thetravel lanes (see Figure 7.28); or

• other kerb types are used and the design hourlytraffic volumes can be accommodated in onetravel lane and separate right turn lanes areprovided for significant turning volumes.

Where signalised intersections are proposed,medians need to be wide enough to accommodatesignal posts, lanterns and servicing facilities. Adesirable median width of 2.4 m (for maintenanceladder spread) should be provided. Atintersections other than six lane dividedcarriageways with right turn storage lanes, (i.e.locations with three lanes or less at the stop line),the minimum median width of 1.2 m may beapplied, provided that all intersection movementscan be adequately controlled by overhead lanternson mast arms.


7

Table 7.10 gives a guide to recommended widthsfor medians on urban roads. Typical treatments areillustrated in the Typical/Cross Sections in Figure7.6.

Table 7.10 Urban Road Median Widths

Total Residual RightMedian Median TurnWidth Lane

Desirable 5.9 2.4(1) 3.5

Minimum 4.3 1.2(2) (4) 3.1

Minimum 1.6 1.6(4) -(Future traffic barrier,no right turn bays or (4.0) (4.0)(3)

significant pedestrians)

Absolute 0.9 0.9 -Minimum(No right turn bays, notraffic barrier, no trafficsignals)

Notes:(1) Where traffic signals are proposed, the median

width is to continue for a minimum of 3 m each sideof the central traffic signal post.

(2) 1.2 m allows for single lantern traffic signal display,minimum pedestrian storage and clearance tosigns. 1.5 m allows for dual 200 mm lantern display.

(3) Where two stage mid-block signalled pedestriancrossings are required, the desirable width forpedestrian storage is 4 m.

(4) Where pedestrians are likely to accumulate onmedians the width should be a minimum of 1.5 to2.0 m.

Tips for Treatment of Urban Medians

• Narrow medians and noses of medians atintersections should generally be treated with a"hard" surface. A most effective treatment isstamped concrete (or similar) in an appropriatecolour (often terracotta).

• Exposed aggregate treatment should be avoidedbecause the slurry from the process is washedinto pipes and waterways thereby causingblockages and/or environmental harm

• Where bedding sand is used under bricks orpavers or concrete slabs, the sand must betreated with a suitable poison to avoidinfestation with ants, which create voids underthe paving.

• It is preferable to use 5 or 7 mm aggregate asthe bedding medium for bricks and pavers, orconcrete slabs.

• Where landscaping is used in medians it ispreferable to use hardy species that do notrequire extensive watering once established.(Refer to Metropolitan District for guidelineson their experience.)

• If watering is required, care is required inselecting a suitable system. “Keeping it simple”appears to be the most effective way (e.g.providing watering points in the form of taps inpits in the areas requiring watering). Automaticsystems can cause difficulties and must bemonitored closely.

• Consideration should be given to safepedestrian use of raised medians wheredrainage channels are specified to facilitatecross median flows of pavement runoff. Inurban areas, it is not unreasonable forpedestrians to cross the road using the medianas a refuge. Drainage slots pose a hazard topedestrians due to a sudden step down from themedian surface. Wherever possible, the use ofmedians with drainage slots as a pedestrianrefuge should be avoided. However, if this isnot possible then the following solutions maybe considered to improve safety forpedestrians:

- delineation of the edges of the drainage slot

- making the drainage slot wider (it thenbecomes a clear step down and step up)

- edging the slot with mountable kerb orsimilar sloped edge

- replacing the slot with a small box channel

- covering or plating the slot

- fencing the median to discourage pedestrianuse.

Replacing the slot with a box culvert orcovering/plating the slot is not recommended asthis may result in a maintenance issue.

September 2004 7-25


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7-26 September 2004

7.4.4 Motorways

Where possible, the median provided formotorways should be as for rural roads above. Inconstrained urban situations, narrower mediansprovided with barriers may be appropriate. Thewidth available for the median will dictate thetype of barrier to be used based on the deflectionof the barrier type chosen but the various types ofbarrier do have minimum width requirements.Details are provided in Chapter 8.

If future widening is likely, the widening shouldbe applied on the median side of the carriageways.Therefore, the width of the median in the firststage should be such that the width after wideningmeets the minimum width required. Desirably,this should be at least 15m to provide the safestsituation. In constrained cases, however, theminimum will be that required to accommodate aconcrete barrier with a clearance of 2.0m (3.0mfor 3 or more lanes) to the face of the barrier. Thisprovides for the “shy line” distance on the medianside (see Table 7.1).

Extensive use of concrete barriers is not apreferred option on environmental grounds andthis should be considered when determiningmedian widths.

7.4.5 Clearance to Medians

In a lit area with a design speed of 80 km/h or less,no lateral clearance is required from the edge oftravel lane to a raised median (i.e. one with amountable kerb). However in an unlit speed zoneof 80 km/h or less, a 0.5 m lateral clearance isrequired to a raised median. The gutter adjacent tothe kerb face, if provided, is located outside thelane.

In areas where the design speed is greater than 80km/h and no street lighting exists, a lateral offsetof 1.0 m is required, measured from the edge ofthe lane to the bottom face of the kerb (Types 8 -15). If lighting is provided, the clearance may bereduced to 0.5 m.

7.4.6 Rural Median Treatment

In rural areas, depressed medians are preferredand a width of 15 m is the desirable minimum.Where a distance of 15 m cannot be achieved,acceptable widths are those that provide anacceptable clear zone width for traffic in eachdirection between the edge of travelled lane andthe edge of verge of the opposite carriageway. Ifthis width cannot be achieved, median barrier maybe required (see Chapter 8).

In depressed medians, slopes of 1 on 10 arepreferred with a maximum preferred slope of 1 on6. A slope of 1 on 4 should only be adopted inconstrained areas. Landscaping or fencing may berequired to prevent U-turns if safety barrier is notused.

Longitudinal drainage of medians should drainfrom both sides to appropriate gully pits (i.e. noblocks). Where blocks, levees, median cross oversand the like are required, the slopes facing trafficshould be 1 on 20 (1 on 6 absolute maximum).Where longitudinal culverts are required in themedian (e.g. under a cross over), the ends shall besloping (1 on 6 maximum) and provided withparallel bars at right angles to the traffic.

Longitudinal culverts in the median should beavoided if at all possible. A much betterarrangement is to collect the water in a drop inletand dispose of it to the roadside or into adjacentcross drainage installations.

In general, medians should be kept clear ofobstructions within the clear zone requirements ofthe road. Designs should avoid the use of headwall, unprotected culvert openings, solid signfoundations, non-frangible sign posts and lightpoles in the median. Planting should consist of“frangible” species of ultimate trunk diameter notgreater than 80 mm unless it is outside therequired clear zone and/or is located behind theappropriate barrier. Landscaping design andspecies selection will depend on the specificcircumstances and requires specialist input.

The design of the median should ensure that it isas maintenance free as possible. This willminimise the amount of time that maintenance


7


personnel will be required to spend on the medianthereby reducing their exposure to traffic hazards.

Features limiting the horizontal sight distance oncurves must be located such that adequate sightdistance is achieved. Offsets needed to achievethis are given in Figure 7.6.

Figure 7.6 shows a range of acceptable treatmentsfor medians in rural areas. More details are shownin the Typical Cross Sections given in Section 7.12.

7.5 Verges, Footpaths andOuter Separators

7.5.1 Verges

The area between shoulder and batter hinge pointis the verge and is used for installation ofdrainage, guardfences, and batter slope rounding.

The recommended minimum verge width on anembankment with guideposts is 0.5 m and with anon-rigid safety barrier, 1.0 m. At difficult sitesthe verge may be narrowed to 0.75 m for safetybarrier placement, however special foundationtreatment will be required to ensure that thematerial behind the safety barrier providesadequate support for the system.

Table 7.12 shows the recommended verge widthsand Figure 7.7 shows typical cross sections ofvarious verge treatments.

Table 7.12 Recommended Verge Widths

Formation Verge FunctionConfiguration Width (m)Embankment 0.5 Min. rounding, with

space for guide posts0.75 Minimum verge for

non-rigid safetybarrier (special casesonly)

1.0 Desirable rounding,min. verge for safetybarrier

1.0 to 3.0 Safety barrier flareand anchorage

Cutting 2.0 min Table drain1.5 min Concrete lined drain

Generally verges are not provided in urban areas.However, if a situation arises where they arerequired, then the verge widths specified in Table7.12 should be adopted.

7.5.2 Footpaths

Generally, footpaths provide room for:

• Pedestrian movement;

• Bicycle travel;

• Public Utility Plant (PUP) installations;

• Turning movements between the carriagewaysand adjacent property entrances;

• Road signs and lighting standards;

• Landscaping; and

• Bus bays.

Width

The minimum footpath width to be adopted is 2.0m. This will provide 1.5 m for pedestrians plus anallowance for lighting standards and road signs.However, much greater widths are required asstandard dimensions, particularly in commercialand industrial areas and on Arterial Roads.

This is because the width required for the PublicUtility Plant allocations is usually much greaterthan that required for the pedestrian movement. Aminimum width of 3.6 m is required for thesereasons and greater widths are sometimesnecessary. Detailed footpath requirements shouldbe determined in conjunction with the relevantLocal Government and Public Utility PlantAuthorities.

Table 7.13 sets out desirable widths for footpathson Arterial Roads. Any residual road reserveshould be allocated to the footpath to provideadditional space for landscaping and driveways.

September 2004 7-27


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7-28 September 2004


7

1.0 1.0

rounding rounding

Rounding or gutter

1 on 4or flatter

1 on 4or flatter

Dependently aligned with depressed median

9.0 minimum

0.5

1 on 4or flatter

rounding

1.0

Independently aligned with single slope median

1.0 1.0

*

Minimum median

*

* Allowance for dynamic deflection of barrierneeds to be considered. See Chapter 8.

1.0 1.0

Landscape treatment on right hand curves (see Table 7.11)

#

Mature bushes

# Refer Chapter 11, Section 11.(Table 7.11 provides an example for 110km/h)

Curve Radius(m)

Table 7.11Offsets for Sight Distance at 110km/h

Offset110km/h (m)

800

1000

1500

2000

5.5

4.0

2.0

2.0

2

2

1

Notes:1. Based on median lane width of 3.5m.2. Minimum for shy line.

Figure 7.6 Median Treatment


7

Shoulder 1.0m (min)

Embankment (showing safety barrier location)

CrossfallHinge Point

Rounding

Verge 1.0m (min)Batter

Shoulder 1.0m (min)

Cutting (unlined table drain)

Crossfall

Hinge Point


Table drain invert should be below thedesign sub-grade level to ensuredrainage of the pavement layers.

Type 22/28 channel may beused within the roadshoulder. Where cyclistsare provided for, shoulderwidth must be in accordancewith Section 7.3.8.

1 on 4

* See Section 7.9.1

0.1m

*Table drain

Shoulder 1.0m (min)

Cutting (concrete lined table drain)

Crossfall

Concrete 0.1m thick


1 on 10

Hinge Point

Berm

(var.)

Type 22/28

0.5m

Figure 7.7 Typical Sections Detailing Verge

7-30 September 2004

If kerbed footpaths are not provided thensufficient verge width should be available toenable pedestrians to walk clear of the roadcarriageway (i.e. lanes and shoulders) preferablyoutside the clear zone.

For shared pedestrian/bike paths, refer to Chapter5, Section 5.5.4.

Table 7.13 Desirable Widths for Footpaths onArterial Roads

Road Type Footpath Width (m)Residential Commercial

and IndustrialUrban Arterial Roads 5.5 5.5Other Urban Roads 4.0 5.5Based on:• 4.0m - Services Requirement. Where a footpath is

wider than 4.0m, the services allocation shouldremain at 4.0m.

• 5.5m - Bus Bay and Landscaping Requirement. Inorder to maintain capacity on major urban roads,bus bays should be provided where possible withinthe footpath width. A 5m minimum footpath width isnecessary at the bus bay site. Between bus baysites, the width surplus to services requirementsmay be allocated to landscape planting.

Footpaths and Driveways

Many councils have minimum designrequirements which should be considered for theprovision of footpaths.

Typical driveway crossings for high and low levelfootpaths (to be used as a guide in the absence oflocal council regulations) are given in Figure 7.8.

Depressed footpaths introduce drainage problemsand therefore should only be considered whereaccess conditions or the high costs involved inproperty and utility adjustments restrict alterationto the existing footpath levels.

A desirable verge side slope of ±1 on 6 may beused at locations adjacent to parks, reserves etc.where driveways are not required.

In difficult terrain this side slope may be increasedto ±1 on 5.

Vehicle templates for standard large and smallpassenger cars should be used to ensure that thesevehicles can use the driveway without bottomingon any part of it (see Appendix A).

Public Utility Plant (P.U.P.) Allocations

Public Utility Plant is usually located under urbanfootpaths in accordance with standards negotiatedbetween the various Local Governments and theService Authorities. While some degree ofstandardisation has been achieved, there aredifferences between Local Governments and theactual distribution in any area will have to bedetermined for that area.

Some typical space allocations are shown inFigure 7.11(a). These are taken from the StandardDrawings prepared for the then Institute ofMunicipal Engineering Australia, QueenslandDivision in 1995. All cases must be treated ontheir merits and the advice of the relevant LocalGovernment obtained to ensure that the standardpractice for the area is implemented.

Figure 7.11(b) also provides information ontypical depths of cover to services under roads andfootpaths. Table 7.14 sets out nominal depths ofcover for the various utilities. This information isprovided as a guideline only and specific detailsmust be obtained from the relevant Authority forall projects. Notwithstanding the cover given inFigures 7.9, 7.11(b) and Table 7.14 under roads,for crossings under declared roads, the minimumcover (unless otherwise approved) is to be:

• 600 mm below the invert of table drains;

• 1200 mm minimum below the existing orfuture roadway;

• 600 mm elsewhere;

provided that there is also a minimum cover of300 mm below the level of the existing orproposed sub-grade.


7

September 2004 7-31


7

* See Figure 7.21 for details.# Required for wheel chair access (Australian Standard AS 1428.1).Figure 7.8 Typical Driveway FCrossings

TYPE 1ANEW ROADWAY (AFTER PAVEMENT CONSTRUCTION)

LV (240V)

New Road Pavement

Lean mix concrete*

Bedding sand*

Marker tape

75 min

75 min

450 min*

50 min 50 min

25 min

500

min

*

New Road Surfacing

* See Standard drawing 1149

Refer also to Standard Drawing 1149 Ducts for Underground Electrical Conduit• New and Existing Roadways; • Bored Crossings; • Single and Multiple ConduitsFigure 7.9 Installation of Underground Conduits within the boundaries of Declared Roads

7-32 September 2004

Designers must consider the potential to protectexisting PUP rather than relocating it when aproject changes the road alignment. For example,a Telstra access chamber could be left under thepavement and an access provided from thefootpath rather than relocating the wholestructure.

Appropriate risk assessment should be undertakentogether with consultation with the appropriateAuthorities, to determine the most economicalsolution. The resulting plan must be approved bythe relevant PUP Authority.

Overhead services require special consideration -see Section 7.10.7 for details.

7.5.3 Outer Separators

General

An outer separator is the portion of road reserveseparating a through carriageway from a serviceor frontage road, as shown on Figure 7.10.

Figure 7.10 Outer Separators

7

Table 7.14 Nominal Depth of Cover for Various Utilities

Cover Electricity Gas Communications WaterFootway Roadway Footway Roadway Footway Roadway Footway Roadway

300 Communicationcables in

shared trench450 Communication Urban Urban Local Local

cables in 500kPa network networkshared trench cables & cables &

conduits conduitsphone/ phone/pay TV pay TV

500 Rural 100m pipeIntermediate

sizes forDICL

600 LV cables LV cables 500kPa Other Other 740mm pipe 100mm pipenetwork network Intermediate Intermediatecables & cables & sizes for sizes forconduits conduits UPVC & GRP DICL

700 750mm pipe750 HV cables to HV cables to 1000kPa Rural 100mm pipe

22kV 22kV 500kPa Intermediatesizes for

UPVC & GRP900 HV cables to HV cables to 1000kPa 750mm pipe

33kV & above 33kV & above1000 750mm pipe1200 3500kPa 3500kPa

Note: DICL Ductile Iron Cement Lined UPVC Unplasticised Poly Vinyl ChlorideGRP Glass Reinforced Plastic

WARNINGThis Table shows nominal laying depths of services by various Authorities and is for information only.

EXISTING SERVICES MAY BE LAID AT DEPTHS AND LOCATIONS OTHER THAN THOSE MENTIONED.It is important that consultation be made with the respective utility Authorities for an indication of the presence of a service.

Hand excavation to determine the exact utility location is advised prior to using any mechanical equipment.

September 2004 7-33


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Figure 7.11 (a) Typical Service Corridors and Alignments

7-34 September 2004


7

Figure 7.11 (b) Typical Service Conduit Sections

Outer separators:

• separate and act as a barrier between trafficflows on the through carriageway and aservice/frontage road;

• provide visual separation of the two flows;

• provide headlight glare screening especiallywhere the service road carries two way traffic;

• provide walking or standing space forpedestrians;

• accommodate roadside planting;

• accommodate guard rails and other barriers,fencing, lighting poles and signs;

• accommodate differences in levels between thethrough carriageway and the service road;

• provide space for bus bays;

• accommodate service installations in specialcases (primarily “trunk” services when thenormal footpath allocations are already used);

• reduce the number of conflict points likely tooccur through the number and frequency of useof property access points between successiveintersections; and

• eliminate the need to provide parallel parkingon the through carriageway, thereby increasingthe capacity of the through carriageway.

Widths

Table 7.15 provides typical widths that will meet arange of circumstances. These tend to be theminimum required to meet those circumstances andit is desirable to use greater dimensions if possiblein the space available. When allocating space to thevarious components of the cross section, areasonable balance between the competing needshas to be maintained. For example, where trafficsignal control is to be used at intersections, extrawidth available is better allocated to the outerseparator than the median once the minimum needsof the median have been met.

However, it is desirable that an outer separator beof sufficient width to absorb level differencesbetween the through carriageway and the service

road and also to allow parking in the service road.

In rural areas, an outer separator width of 15m isdesirable, particularly where the service road istwo way.

Table 7.15 Typical Widths of Outer Separators

Factor Situation Width (m)(excludingshoulders)

Physical Safety barrier with or 0.5Separation without glare screen

Safety barrier with kerbs 1.0on both sides

Visual Two way operation on Light traffic on Separation service road with no service road:

artificial glare screen 5.0Medium to heavy

traffic:>7.0Headlight Planting shrubs as 2.0 - 5.0Glare the screenScreening Artificial Screen 0.5 - 1.0Pedestrians Occasional usage or if 2.0Cyclists part of a designated

bicycle routeShrubs for screening 4.0(including walking space)Trees and Shrubs 4.0 - 5.0

Space for Safety barrier, fencing, 0.5 - 1.0Roadside lighting standards etc.FurnitureBus Bays Indented into outer 6.0

separator (min. 5.0)Intersections Traffic Signal Control 2.4 min.

Note: Where safety barrier is used, allowance fordeflection must be made.

Slope

Where outer separator side slopes exceed 1 on 4or 1.0m in height, safety barrier protectionadjacent to the higher of the two roads, may bewarranted.

At intersections where traffic signal control isproposed, the outer separator should have amaximum side slope of 1 on 8 maintained for atleast 3 m before and after the signal post.

September 2004 7-35


7

7-36 September 2004

7.6 Clear Zone

7.6.1 General

The intent of the clear zone is to provide space forthe driver of a vehicle that runs off the road toregain control while sustaining minimum damageto the vehicle and its occupants. It is the width ofroadside, beginning at the edge of the travelledway, that is available to the driver to take thisaction.

This zone will depend on the location of thevehicle at any point along the road and isdetermined for both sides of the vehicle (righthand side for medians). Accordingly, the clearzone distance is related to predicted trafficvolumes and speed (see Figure 7.12), and takesinto account the widths of adjacent lanes,shoulders, medians, verges, footways andtraversable batters. See also Figure 7.1 and Table7.21.

7.6.2 Guidelines

To be regarded as part of the clear zone:

• the area should be:- relatively flat, with a maximum side slope

of 1 on 3 (cutting) and desirably 1 on 4(embankment) or flatter; and

- traversable, having slope changes that willkeep all wheels of an errant vehicle incontact with the ground (this assists thedriver of an errant vehicle to regain control).See Figure 7.16 for determining appropriaterounding for traversable batter slopes withinclear zones.

• the area should be kept clear of all large, fixedobjects (such as species greater than 80mm inultimate trunk diameter, structure support piers,culvert headwalls, large solid [i.e. non-frangible] sign support structures, non-traversable gutters and barriers) which are ofsuch a size that they cause unacceptable rapiddeceleration rates to the occupants of animpacting vehicle. Only objects which willcollapse or break away on impact should belocated in the clear zone to ensure minimal

damage to an errant vehicle and its occupants.

• the desirable width of a clear zone is dependenton predicted traffic volumes, traffic speed androad geometry.

Figure 7.12 is a nomograph that allows for theappropriate clear zone distance to be determined.These distances represent a reasonable measure ofthe degree of safety appropriate for a particularroad and must be balanced by comparing land useand costs. The widths given are approximate onlyand the nomograph should not be used to infer adegree of accuracy that does not exist.

Where it is not possible to provide an adequateclear zone, free of non-frangible obstacles for theappropriate distance, a safety barrier should beconsidered in accordance with Chapter 8 of thismanual.

The provision of a clear zone is often betterpractice than the erection of a safety barrier (dueto the length of the safety barrier generallyrequired).

7.7 Crossfall

7.7.1 General

Crossfall is defined as the side slope, normal tothe alignment, of the surface of any part of thecarriageway. Crossfall is provided primarily tofacilitate pavement drainage.

The usual arrangement for straight sections ofroad is for the pavement crossfall to slope downfrom either the centreline or the median.However, the designer should not be limited tothis arrangement as inwards sloping crossfall, orone way crossfall may be useful for certaingrades, drainage or side slope situations.

For wide multilane pavements, it may beappropriate to crown the pavement with one ortwo lanes draining to the median. This minimisesthe depth of flow on the pavement surface,reducing aquaplaning potential.

On curved alignments, the carriageway may slopeupwards from the centreline or median to help


7

September 2004 7-37


7

Figure 7.12 Clear Zone Nomograph

7-38 September 2004

counteract the centrifugal forces on a vehicletravelling around the curve. This form of crossslope is known as superelevation. Chapter 11details the amount of superelevation required oncurves of varying radii, and the methods ofsuperelevation development.

Changes from one crossfall to another shall betransitioned over a length to satisfy the rate ofrotation and relative grade requirements given inChapter 11. Sufficient dimensions, levels, cross-sections and/or profiles should be provided on theconstruction drawings to enable the design to beaccurately reproduced in construction.

7.7.2 Crossfall and Drainage

Crossfall has the important function of sheddingwater from the roadway to reduce the possibilityof a vehicle aquaplaning in wet conditions.Details of the relationship between crossfall andpavement drainage design are given in the RoadDrainage Design Manual (Main Roads, 2001).

7.7.3 Road Crossfall

Typical crossfalls, depending on the type of roadsurface are shown in Table 7.16.

Table 7.16 Typical Pavement Crossfalls

Road Surface Traffic Lane Shoulder(%) (%)

Cement Concrete 2.0-3.0 2.0-4.0Asphaltic Concrete 2.5-3.0 2.5-4.0Sprayed Seal 3.0-4.0 3.0-4.0Unsealed 3.5-4.0 4.0-5.0Within Floodways 1.0-2.0 1.0-2.0

There are many controls in urban areas whichforce departures from the above values.

Differences in levels between kerb lines cansometimes be taken up by offsetting crown lines oradopting one-way crossfalls (see Section 7.7.6).

If it is necessary to increase traffic lane crossfalls

above those given in Table 7.16, then themaximum sustained crossfall should not exceed4%; local increases to 6% are acceptable, but onlyin extreme cases. Stability of high vehiclesbecomes a problem on crossfalls greater than 6%.Clearance of high vehicles to poles, signs, etc.should also be checked (see Section 7.10.3).

Crossfall should be provided on right turn lanes ina manner that ensures that the bay is adequatelydrained, and minimises the amount of water at themedian nose area.

Multicombination Vehicle (MCV) performance isinfluenced by crossfall. The crossfall on freightroutes should not exceed 3%.

However, on low trafficked roads where bettersurface drainage is required to protect low qualitypaving material, a crossfall of 4% has been usedsuccessfully. This crossfall also tends toencourage MCVs to travel closer to the centre ofthe pavement with a consequent advantage ofreducing damage to the pavement edges.

Cross-over Crown Line

On straight sections of road, the maximumalgebraic change in crossfall over a crown line is7%.

Where a turning roadway exits from acarriageway, and a different crossfall is requiredon the through road and the turning roadway, thealgebraic change in crossfall over the crown lineformed must be limited to the values shown inTable 7.16 (a).

Table 7.16 (a) Difference in Crossfall at CrossoverCrown Line - Turning Roadways

Speed Max. algebraic difference inkm/h crossfall at crossover

crown line, %< 30 Determined by vehicle clearance

30 - 50 6> 50 5

Turning roadway with tapers:speed = ‘average running speed’ of through road

Turning roadway without tapers:speed = design speed of turning roadway


7

Turning speeds for various combinations of radiusand crossfall are shown in Chapter 13, Figure13.38. It is preferable to limit adverse crossfall to-3%, with an absolute maximum of -4%.Maximum positive crossfall on turning roadwaysis 7% (see also Chapter 13, Section 13.8.2.1).

For a turn executed at very slow speed (say <10km/h), the desirable maximum adverse crossfallshould be -5% with an absolute maximum of -7%.

7.7.4 Median Crossfall

Medians up to 8 m wide are generally level orfollow the crossfall of the road. Depressedmedians greater than 8 m wide should have adesirable crossfall of 1 on 10 (see also Section 7.5,Figure 7.6).

At intersections where signals are to be installed,the median cross slope must match the slope ofthe road through the intersection and should notbe greater than 6%.

7.7.5 Footpath Crossfall

It is usual to slope the footpath towards the roadso that water does not drain on to adjoiningproperties. Where it is not possible to do this,drainage onto adjacent properties will have to bearranged with the property owners. It is notusually an issue in rural areas.

The design of the footpath requires considerationof several factors:

• Drainage across the footpath;

• Pedestrian requirements for a walkway;

• Use by wheel chair bound people; and

• Requirements for visually impaired people.

Drainage is best served by a crossfall of 3% butthis conflicts with the need to accommodatewheel chairs. A maximum crossfall of 2.5%should be adopted to accommodate wheel chairs -2% is preferred (see AS1428.1). In thesecircumstances, care will be required to ensure thatwater does not accumulate on the walkway orbecome a hazard to people with disabilities.

Provision for visually impaired people should bein accordance with Australian Standard AS 1428.4.

Figure 7.13 illustrates these requirements.

7.7.6 Parking Lane Crossfall

In general, the crossfall on the parking lane shouldbe the same as the through lanes, but in somesituations the crossfall may be varied. Themaximum crossfall of the parking lane should be5%. The maximum algebraic difference betweenthe through lane and parking lane should notexceed 8%. (Reference - Qld Department of MainRoads: Urban Road Design Volume 1, 1975 -Chapter 3 and Main Roads Deparment Qld -Road Design Manual Volume 1 - Chapter 7.)

7.7.7 Crossfall Configuration onSide Slopes

Where there are significant differences in levelsbetween opposite sides of a road, many problemsoccur with conventional design includingrestoration of access and costly adjustments toproperties or public utilities. An option to consideris to adopt a one way crossfall.

In these circumstances the one-way crossfallshould not exceed 4% (3% is preferred). Foraesthetic reasons the slope should extend fullwidth between gutters (from lip to lip, includingthe median). However, if drainage into the gutteron the high side is considerable, the crossfall ofthe kerbside lane can be reversed to a maximumof 4% to increase the gutter capacity. Theresulting break in the crossfall is called an offsetcrown and is usually located at the offside edge ofthe kerbside lane. The development of the offsetcrown requires careful design to avoid having thecrown cross vehicle paths. Figure 7.14 shows bothdesirable and undesirable methods of developingan offset crown.

Whilst a one-way crossfall design is oftensatisfactory in sloping country, there are areaswith steep slopes where this method will not meetrequirements. Under these conditions it maybecome necessary to consider other solutions,

September 2004 7-39


7

7-40 September 2004

such as providing parallel service roads or splitlevel carriageways.

Widening Two Lane Roads - OffsetCrown

Where an existing two lane road is to be widened,it may be more economical to widen on one side,retaining the existing crown of the road. This willresult in an offset crown to one side of the newcentre line. Provided that the offset crown is notmore than 1.5m from the new centre line, thisresult is acceptable. The crown line in thesecircumstances is barely perceptible to the driver.However, where the offset crown is closer to theedge line than the centre line, the effect isdisturbing to the driver and is unacceptable.

7.7.8 Split Level Carriageways

In extreme cases of side slope it may be necessaryto adopt a split level carriageway by providing asteep batter or retaining wall in the median.

Attention needs to be given to the followingdesign aspects of split level carriageways in urbanareas:

• provision for pedestrians;

• access for local traffic;

• the design of intersections;

• the provision of traffic signals, and

• the provision of a central traffic barrier.

For rural situations, attention must be given to:

• access for local traffic;

• the design of intersections; and

• the provision of a central traffic barrier.


7

Figure 7.13 Footpath Crossfalls

7.8 Batters

7.8.1 Batter Slopes

Batters are the side slopes of cuttings andembankments. The slope is expressed as a ratio,one unit of vertical rise on the horizontal distanceX (1 on X).

Maximum slopes are determined from thegeotechnical properties of the materials involved.Consideration should be given to the followingfactors when selecting batter slopes:

• the test results and any recommendations givenin the geotechnical report;

• the effects of long term exposure to theelements (weathering) on the stability of thecutting;

• lining the catch drains to minimise failure ofthe cutting by the leaching of fines through theexposed cut face;

• erosivity of the batter soils;

• the ease and cost of maintaining the adoptedbatter slope;

• traffic safety and possible economy byeliminating safety barriers and using flatterslopes;

• appearance and environmental effects, and

September 2004 7-41


7

Figure 7.14 Development of Offset Crown

7-42 September 2004

• the overall economy of the project.

Slopes flatter than the maximum should be usedwhere possible. Generally flatter batter slopes aresafer, more resistant to erosion and have a betterappearance. The cost of stabilizing, planting andmaintaining steep slopes may exceed the cost ofthe additional earthworks and road reserverequired to provide a flatter, possibly traversableslope. Flatter slopes also reduce the extent ofsafety barrier and reduce potential environmentalimpacts (erosion and sedimentation). However,the impact of flatter batters must be balancedagainst the desirability of retaining significantnative flora, other environmental issues andproperty impacts.

Maintenance vehicles can work on slopes up to 1on 3 but 1 on 4 slopes should be used wherepracticable.

On cut and fill slopes less than 1m high, battersnot steeper than 1 on 6 are preferred.

For initial planning adopt slopes of 1 on 3 to 1 on4 for heights of cut (excluding rock) and fill up to2.0 m (3.0 m on Highways and Motorways).Above these heights, 1 on 2 may be adopted but itis preferable to use 1 on 3 maximum whereverpracticable at the planning stage. Actual slopesadopted in design must consider all of the factorsdiscussed.

Fill Batters

In addition to the general requirements set outabove, it is desirable for fill batters to be as flat aspossible. Fill batter slopes flatter than 1 on 4 (1 on6 preferred) should be used wherever practicable.The maximum fill batter slope should be nosteeper than 1 on 2 (1 on 3 preferred) to assistrevegetation. Where practicable:

• adopt 1 on 4 slopes wherever mowing isrequired, and

• flatten batters as a preferred treatment toproviding guardrail.

Where excess spoil is available, consider flatteningthe fill batters to 1 on 6 over the width of the clearzone, increasing the slope beyond the clear zone to

a maximum of 1 on 3. Alternatively, a continuousflatter slope not steeper than 1 on 4 could be used.

Cut Batters

Earth cut batter slopes should not exceed 1 on 2unless the constraints are such that a steeper slopeis required and the Geotechnical investigationshows that steeper slopes are stable.

In rock cuttings:

• adopt an absolute maximum slope (subject togeotechnical acceptability) of 1 on 0.25;

• place benches at suitable locations in cuttingsover 10 m high (see 7.8.4);

• provide access through any debris barrier toassist removal of debris;

• provide appropriate clearances between the topof the batter and other obstructions and theboundary to assist maintenance includingcollection of debris from cutting slopes;

• provide catch banks at the top of the batter.

7.8.2 Traversable Batters andBatter Rounding

Rounding at tops of cuttings and embankmentscan reduce scouring, remove loose material andimprove the appearance of the road. The amountof rounding on the top of cuttings usually dependson the material, the depth of rock (if any) and thenatural contours of the ground.

Traversable embankment batters assist byproviding an errant vehicle an opportunity torecover and return to the through carriageway, bymaintaining all wheels in contact with the ground.

Traversable batters shall have the followingattributes:

• embankment batter slopes of 1 on 4 or flatter;

• cutting batter slopes of 1 on 3 or flatter;

• roundings shown in Figure 7.16 or greater athinge points;

• channels with 1 on 4 slopes or flatter.


7

1 on 3 embankment slopes can be traversed byvehicles but it is unlikely that it can recover onthat slope - 1 on 4 accommodates recovery. On cutbatters, the 1 on 3 slope directs the vehicle back tothe road and therefore allows for recovery. A 1 on4 slope allows this manoeuvre to be undertakenwith better control than on the 1 on 3 slope.

Where batters have a potential impact severity of3 or more (refer to Chapter 8), the surface finish isto be free of elements that may snag componentsof errant vehicles, causing them to yaw (spin) atunacceptable rates. The batter slopes are to beformed similar to accepted safety barrier shapes,especially at the entrance to cuttings.

7.8.3 Batter Slope Treatment

Variable batter slopes can be used to improve aroad’s appearance by blending it into thesurrounding terrain. This treatment can smooththe transition between cutting and embankment,assisting the provision of lay-by areas.

Common treatments adopted are constant batterslope or constant batter catch point type. Constantbatter catch points are preferred because of theimproved appearance by blending various slopebatters into surrounding terrain. Catch points at aconstant distance (8m suggested) from theformation edge in light earthworks or at the endsof adjoining cuts and fills in heavier earth-workscreate a pleasing appearance at very smalladditional cost and should be adopted whereverpracticable (see Figure 7.15 and 7.15(a) and theRoad Landscape Manual, Main Roads 1998).

The appropriate top and toe of battersurroundings, relative to the road shoulder and tothe natural terrain, are based on the followingassumptions:

• the 85th percentile angle of departure from theroadway by an errant vehicle has been assumedto be 22° (average).

• the batter slope is suitably compacted andgraded, and free of obstacles that may causevehicle snagging.

Figure 7.16 provides the dimensions to be used.

Cut batters often require some form of treatment tominimise erosion and provide for stabilising theslope surface. Revegetation should be encouragedas far as possible. Where designed landscaping isimplemented, the treatments will be defined andmay vary from reasonably flat slopes on whichformal planting is undertaken, to slopes as steep as1 on 2 where hydraulic seeding and mulching maybe carried out. In other cases, revegetation willoccur more readily if the batter slopes areconstructed to hold topsoil and minimise erosion.Stepped (or serrated) batters (as illustrated inFigure 7.17) may often provide the necessaryconditions for revegetation but these should not beused in dispersive soils (e.g. sodic soils). Furtherenvironmental considerations and guidelines fordesigning batters are provided in Chapter 3.

The slope and treatment to be adopted isinfluenced by the type of material encounteredand the available right of way. Figure 7.18illustrates several alternative treatments that maybe used subject to the stability of the slopes andwalls involved.

7.8.4 Benches

A bench is a near horizontal ledge that isconstructed on a side slope to provide sightdistance, slope stability and assist with batterdrainage.

Benches are used on the face of batters to:

• reduce surface water run-off;

• accommodate a change in the batter slope orbatter material;

• provide maintenance access, and

• catch falling debris from the batter face.

The normal width of a bench is 5.0m (with aminimum of 3m), the edges of which should notbe rounded (see Figure 7.19).

Benches are sloped away from the carriagewayand drained towards the ends of the cutting. Thelongitudinal grade of the bench must bedetermined in conjunction with the necessaryerosion control measures.

September 2004 7-43


7

7-44 September 2004


7

Figure 7.15 Batter Slope Treatments

8m

* See Figure 7.7

Superimposed Cross Sections

Formation(including vergeand rounding)

1on

2

Hinge Point *

*

Level

1 on 4

Figure 7.15 (a) Transition of Batters from Bank to Cutting

September 2004 7-45


7

Figure 7.16 Desirable Crest and Sag Roundings

7-46 September 2004


7

Figure 7.17 Treatment of Cut Batters for Revegetation

N.B. • Only suitable for battersbetween 1 on 3 and 1 on 1.

• Flatter batters should betreated by contour rippingand top soiling.

• Steeper batters requirespecial treatment.

• NOT to be used in dispersivesoils.

September 2004 7-47


7

Figure 7.18 Alternative Treatment for Batters (Source: Road Landscape Manual)

Benching

Visual Effect of Steep Cut Slope

Planting at the Base of Steep Slopes

Source: RTA (1993)Rock Armouring Alternative to Fill Slope

Straw Mulching

7-48 September 2004

Where visibility benching is required, thepreferred treatment is to include the bench as awidened table drain with a flat bottom at least 1.8m wide. (Refer to Chapter 9 for more details onvisibility benching.)

See also 7.11.2.

7.8.5 Rock Fall Protection

Where there is potential for rock falling from theface of a cut batter on to the road surface, actionto prevent the rock from rolling on to the surfaceof the road is required. A table drain with a base atleast 1.8m wide would normally be adequate.

However, where a table drain of inadequate widthis to be used, the road should be protected with achain wire fence erected outside the shoulder edgebehind the kerb delineating the shoulder. Figure7.19(b) illustrates this requirement.

7.9 Drainage

7.9.1 Table Drains

Table drains are located within the verges incuttings. Their purpose is to collect surface waterdraining from the carriageway and adjacent cutbatter, carrying the water to a suitable point ofdischarge beyond the cutting. The invert of thetable drain must be lower than the pavement sub-base to allow efficient drainage of the pavementlayers.

Flat bottomed table drains (1.8 m wide for ease ofmaintenance) are preferred. However, this shouldnot be accomplished at the expense of making thecut batter steeper than 1 on 3. Erosion is less inflat bottomed channels and some advantage isgained even if 1.8 m cannot be achieved. Aminimum total verge width of 2.0m (see Figure7.7) provides space for a mower to operate. Forthe worst case, the residual grass length will be90mm longer on one side.

If it is necessary to deepen the table drain, thecutting should be widened so that the maximum 1on 4 side slope is maintained. Desirably the depth

should not exceed 1m.

The minimum longitudinal grade in an unlinedtable drain is 0.5%. However, flow velocities inunlined table drains should not exceed 1m/s.Velocity of flow must be limited to this or liningwill be required.

The arris formed by the side of a table drain andthe shoulder should be rounded to minimisedamage to errant vehicles.

Lined table drains should be used in place ofunlined drains for grades less than 0.5%(minimum 0.2%), or where velocities are likely tocause scouring (1m/s or greater). Lined tabledrains may be formed in the shape of the Type 28gutter as shown on Figure 7.21 or speciallydesigned to suit the conditions.

On both the nearside and the offside of eachcarriageway in a cutting, a 1.0 m wide Type 28drain will be provided if the drain falls within theshoulder. Where superelevation is provided it willbe permissible for the water on the off side to runstraight into the median. However, considerationis to be given to the provision of a Type 28 drainon the offside edge.

7.9.2 Catch Drains and Banks

Catch drains are located on the high side ofcutting slopes behind the batter rounding. Theirpurpose is to intercept the flow of surface andseepage water within the upper soil layer toprevent erosion of the batter face.

Catch drains should be constructed to have arounded or trapezoidal cross section (see Figure7.20), rather than a ‘V’ shaped cross section(which are subject to erosion).

Depending on the runoff velocity, catch drainsshould be stabilized immediately by seeding,turfing, planting in conjunction with jute mesh,bitumen, masonry, rock mattresses or concretelining. Where an un-lined drain is to be used, thedesigner must consider both the long termperformance of the treatment AND the likelyperformance of the treatment during theestablishment period.


7

September 2004 7-49


7

Road Boundary

CatchBank(Preferred Treatment)

For Detailsee Figure 7.20

5.0m

(min 3m)Bench drained toends of cuttings

1 on 10

2-3m up to max.of 7m, or as required

Channel may needto be lined to avoid

erosion

Figure 7.19 Location of Benches in Cuttings

CHAINWIRE FENCE

All posts to haveweather caps

Terminal posts50 NB galvanised pipe

Std. galvanised (Type B)(knuckle / knuckle) chainwiremesh. 50 x 2.5mm

3/4mm helicoil cablewire

Fix chainwire and cablewirein accordance with manufacturers’recommendations.

"S"

0.3

0.05

0.7

min

1

2.0

1.0

11.5Shoulder

2.0

Traffic Lanes

1%

Chainwire Fence(see detail)

450 350

225

75

12

00

Stay posts to end panelsgalvanised pipe

both sides with 32 NBand every 5th panel on

Intermediate posts40 NB galvanised pipe

5.00 CENTRES

M10x90galvanizedhexagonalbolt & nut.

Drill 12 dia.hole in

post andsleeveforbolt.

50

Galvanized SteelSleeve65 NB (50 NB post)50 NB (40 NB post)40 NB (32 NB Stay)

Figure 7.19(b) Rock Fall Protection

7-50 September 2004

In areas where the catch drain is susceptible toscour, the surface water should be interceptedusing a catch bank placed on the natural surfaceon the high side of the batter point. There is noexcavation of the surface to provide the earth forthe bank or to create the drain. The natural surfaceis therefore not disturbed and not exposed toerosion to the same degree.

7.9.3 Dykes

A Dyke is a low, longitudinal mound of earth,asphalt or concrete, provided near the edge ofembankments when it is required to protect thebatters from erosion, by controlling the watermovement off the road pavement surface. It islocated under the guardfence on the lower side ofthe pavement crossfall. Location of the dyke withrespect to the face of the guardrail is critical forsafety reasons. (See Chapter 8.)

7.9.4 Batter Drains

Batter drains are provided on embankments totransport the water from dykes to the bottom ofthe batter.

They are spaced at intervals which meet themaximum flow width criteria. The location anddesign treatment of batter drains are detailed inthe Road Drainage Design Manual (Main Roads,2001).

7.9.5 Kerbs, Channels andAccess Chambers

Kerbs are used to separate areas used by vehiclesfrom areas used by other modes of transport, orareas to be put to other uses. Channels are used tocollect and convey surface drainage to a dischargeor collection point. Kerbs and channel are usuallycombined but may be used as separate elements.Stability of a kerb only element may be an issuewhere the kerb can be impacted by traffic since itcan easily be knocked out of alignment.

The main purposes of Kerb and Channel are to:

• Provide lateral support to the pavement;

• Collect surface drainage and convey it to a pointof discharge;

• Manage a level difference between the footpathand the carriageway;


7

Figure 7.20 Typical Catch Drains

• Act as a longitudinal delineation of the edge ofcarriageways;

• Separate carriageways from pedestrian andcyclist areas; and

• Reduce the width of cuttings by substituting anunderground drainage system for the usual tabledrains.

The principal types of kerb are:

• Barrier - face sloped at 1 on 0.25;

• Semi-mountable - face sloped at 1 on 1.5; and

• Mountable - face sloped at 1 on 7.5.

Barrier kerb has been used to provide a measure ofprotection to pedestrians adjacent to traffic lanesand it encourages drivers to steer clear of the kerb.It is therefore an appropriate type of kerb to use oninner city streets where pedestrians are insignificant numbers and speeds are low.

Barrier kerbs should not be used on high-speedroads, as it is more likely to trip and overturn avehicle that is out of control. These kerbs should beavoided on the outside of low radius curves as itcan contribute to truck rollovers. If kerb andchannel is essential in these cases, sufficientclearance to avoid the outwards tail swing of largetrucks (check with VPATH) must be provided.

Semi-mountable kerbs are the standard type ofkerb and channel used for delineation anddrainage on all intersections.

Mountable kerb is suitable for the outside ofcurves on interchange ramps, on the approachnoses of exposed islands and for the separation ofnormal traffic lanes from special areas intendedfor use by over-dimensional vehicles in mediansor roundabouts.

Figure 7.21 shows the standard shapes, dimensionsand applications of kerbs and/or kerb and channelthat may be used. Designers should use the mostappropriate kerb type for the specific project.

Designers should:

• avoid barrier kerb adjacent to high speedcarriageways;

• provide adequate clearance to mountable orsemi-mountable kerbs if used adjacent to highspeed carriageways;

• avoid or minimise kerbing near safety barriersto improve safety (details of clearancesrequired are given in Chapter 8);

• include 1.5 m (min.) transitions to change fromone kerb type to another (semi-mountable tobarrier; new kerb to existing of a differentshape);

• adopt 450 mm channel where kerb and channelis required unless special circumstances apply;

• provide 50 mm Asphalt Allowance for allbarrier and semi-mountable kerb not installedon a concrete pavement where the trafficvolume is expected to exceed 10,000 veh/daywithin the design life of the project;

• use kerb that includes a backing strip in areassubject to mounting by overdimensional orheavy vehicles;

• ensure that all grates located adjacent to sealedshoulders or bicycle lanes are bicycle safe inaccordance with Australian Standard AS3996.

In general, access chambers should be locatedclear of the carriageway. This provides for easierconstruction of the pavement and removes asource of potential maintenance problems. It isalso safer for workers using the access chambers.

Where it is not possible to locate the accesschamber clear of the carriageway, it shouldpreferably be placed in the parking lane. The caseof existing access chambers located in thecarriageway is discussed in Section 7.5.2.

7.9.6 Floodways

General

Where floodways are used, it is desired to providereasonable uniformity in selecting floodwaywidths throughout the State without limitingconsideration of particular features of one site orlocality in arriving at the appropriate design.

September 2004 7-51


7

7-52 September 2004

Width Range

Long Floodways: The following points refer tofloodways comprising more than an isolated dip(the usual case of a floodway taking flood channelflows):

• The general minimum formation width shouldbe 8.6m, with some relaxation possible onroads under 150 veh/day;

• The general maximum formation width shouldbe 10.0m, unless the additional costs ofachieving full formation width are notsignificant;

• The minimum shoulder protection should be1.0m;

• The maximum shoulder protection should be1.5m;

• The balance between pavement widening andshoulder width should be determined by localconditions. In the general case where shoulderprotection is more expensive than pavingmaterial, the former would tend to the narrowerlimit. In more remote areas where pavingmaterial can be more expensive than an“adequate” material for cement treatedshoulders, the reverse would occur.

The above criteria lead to Table 7.16 of widthranges related to pavement and shoulder widths

(see Section 7.2.2).

Short Floodways: Where the floodway is shortand confined to a main flow channel, especiallywhere sight distance is close to the minimum forthe operating speed of the road, considerationshould be given to providing a full formationwidth floodway.

Safety Barriers/Bridge Rails

Safety barrier will reduce the efficiency of thefloodway in times of flood, but may be desirablefrom the point of view of traffic safety at othertimes. Whether safety barrier should be installedin a particular case should be determined locally,but where associated with a bridge structure:

• when the bridge is full floodway width, and themain channel is shallow, consideration shouldbe given to omitting bridge rails and safetybarrier. However, road edge guide posts may beprovided on the floodway with reflectorisedhazard markers at the bridge abutment;

• when the bridge is narrower than the floodwayor the channel is deep it may be desirable to userails with at least the minimum length of safetybarrier on the floodway approach to the bridge.The conflict of goals i.e. delineation as againstobstruction in flood time cannot be determinedby a general policy but must be decided locallyby consideration of the specific case.


7

Table 7.16 Width Ranges

Pavement Shoulder Formation Floodway (m)Width (m) Width (m) Width (m) Elementary Total

Widths Width4.0 2.5 9.0 7.0 + 2 x 1.0 to 9.0

7.0 + 2 x 0.8 8.6 (1)

6.0 1.5 9.0 7.0 + 2 x 1.0 9.06.0 2.0 10.0 7.0 + 2 x 1.5 to 10.0

8.0 + 2 x 1.0 10.06.5 1.5 9.0 8.0 + 2 x 1.0 9.06.5 2.5 11.5 8.0 + 2 x 1.0 9.0

7.0 2.0 11.0 8.0 + 2 x 1.0 10.0 (2)

7.0 2.5 12.0 8.0 + 2 x 1.0 10.0 (2)

NOTES:1. The general minimum formation width is 8.6m. However, on lightly trafficked roads at the discretion of the District Director this

may be reduced to 7.4 or 8.0m.2. The general maximum is 10.0m. However, where the cost of maintaining the larger width across the floodway is not excessive,

the full width may be maintained at the discretion of the District Director.

7.10 Bridges and Clearances

7.10.1 Road Bridge Widths

Bridges comprise a relatively small proportion ofthe total road length, but they are proportionallymuch more expensive. They do, however, have amuch longer life than other elements of the roadstructure and the width determined for a bridgeshould be based on a longer period of trafficgrowth than for other elements.

Bridge widths shall be determined from Table7.17 or from Table 7.18. Departure from theindicated widths may be required to satisfyparticular situations.

For example, if the bridge is located in or nearbuilt-up areas, or is part of a local or regionalcycle route, it will need to be designed toaccommodate cycle and/or pedestrian traffic. Thismay be in form of wider shoulders or a separatepedestrian facility on one or both sides of thebridge.

On roads with significant numbers of road trains,sufficient width is required to allow two roadtrains to pass safely. This will be particularlyimportant if the bridge is on a curve.

The widths for National Highways shown in Table7.17 are derived from the published Standards andguidelines for National Highways:

• For lengths less than 20m - the carriagewaywidth (see sections 7.2.5 and 7.3.7 for theelements of width);

• Where the AADT across the bridge is expectedto exceed 1000 per lane within 20 years of theworks being opened to traffic - the width of thetraffic lanes plus 2.4m; and

• For all other cases - the width of the trafficlanes plus 1.2m.

In all cases, the needs of cyclists must beconsidered and appropriate allowance made.

The widths for roads other than NationalHighways shown in Table 7.18 are based on thefollowing approach:

• For bridges shorter than 20m in length - thecarriageway width (see section 7.2 and 7.3 forthe elements of width);

• For bridges longer than 20m - the width of thetraffic lanes plus 1.0m clearance each side.

September 2004 7-53


7

7-54 September 2004


7

TYPE TYPICAL USE PROFILE AND DIMENSIONS

Barrier on road surface:

Dykes;

Islands and median

edges at pedestrain

crossings and signals.

Barrier below road surface:

As for 4

Mountable

Mountable with channel

Channel:

Medians and

Table Drains

1

21

5m

in.

300

R25R25

A

C 40

15

0m

in.

25

A BC

65

Bullnose 10

21

5m

in.

600

Chamfer 25

R25

300300

15

0m

in.

40

610

26

5m

in.

R25

50230

R5

R25

50

15

0m

in.

11

5

R5

R25

50230

C

C

110

190

R25

15

0

4040

A

150

R25

20

0m

in.

15

0 C

110

R5

40

A

2

3

4

5

6

&

7

(300ch)

(450ch)

Barrier Kerb and channel:

As for 4

R5

R25

R25 15

0

450 or 600

40110 300 or 450

A

40

15

0m

in.

C

B

REFERENCE POSITIONS: Height referenceA B CLine of kerb Line of channel

Figure 7.21 Standard Kerb Shapes

September 2004 7-55


7

Semi Mountable kerb on

road surface:

Medians and Islands;

embankment margins.

Semi Mountable kerb:

Backing strip on road surface

As for 8 & 9 where over

dimensional vehicles

traverse kerb.

Semi Mountable kerb

below road surface

As for 8 & 9

Semi Mountable kerb

and channel:

Parking lanes, medians where

drainage required.

8

&

9(with AA)

'AA'490

12

5

R25

R225R25

190300x

A

C

DETAIL

'AA'

*

road surface.

min. depth below1

50

300

C

*

12

5

R25

R225

R25

190110

A

300

C

12

5

R25R225

R25

190110

ADETAIL

'AA'

x

14

&

15

(300ch)

(450ch)

10

&

11(with AA)

12

&

13(with AA)

R225

R25

1104

01

50

min

.

Chamfer 25

R75 12

5

300 or 450C

BA

600 or 750

190

WITH CHANNEL

“AA” = Asphalt Allowance

XDETAIL

R25

10


16

&

17

(300 ch

or

tray)

(450 ch

or tray)

Ramped vehicular

crossing:

Accesses to property

300

600

15

26

0m

in.

the scheme

as specified in

Channel or tray

documents

12

5

300

15

0m

in.


7-56 September 2004


7 Ramped pedestrian

crossing

18

19

20

21

(*BK & 300 ch

or tray)

(*BK & 450 ch

or tray)

(*SMK & 300 ch

or tray)

(*SMK & 450 ch

or tray)80

min

.

15

0m

in.

in the scheme

documents

100

45°

Channel or tray

as specifiedBarrier kerb shown. Details similar for semi mountable kerb

1 on 8 max. #

* BK = Barrier Kerb

* SMK = Semi Mountable Kerb

# Max. ramp slope for wheelchair access shall be 1 on 8.

TYPE

22Channel Adjacent to

shoulders

R751

50

min

.

300

R15

1 on 12

17

5m

in.

1 on 12

25

300

23

24

(300 tray)

(*BK & 300 ch

or tray)

&

Barrier Kerb and Tray:

Medians and Islands

adjacent pedestrian

crossings and signals

R5

#

C

BA

450 or 600

#

Chamfer 25

15

0m

in.

300 or 45040

R25

Gradient 3%

15

0

110

R25

14 (450 tray)

9 (300 tray)

TYPICAL USE PROFILE AND DIMENSIONS


September 2004 7-57


7

Semi Mountable Kerb

and Tray

Medians and

Island

Dished Crossing

Dished Crossing increased

waterway

21

5m

in. R 25

A

300

9

Chamfer 25

15

0m

in.

65

Gradient 3%B

C300

Bullnose 10

600

BA

600 or 750

R25

300 or 450

15

0m

in.

R75R225 12

5

190110

C

#

Gradient 3%

Chamfer 25

25

&

26

(300

tray)

(450

tray)

27

28


500

10

0

1000

500

15

0

min

# 9 (300 tray)

14 (450 tray)


7-58 September 2004


7

Table 7.18 Bridge Carriageway Widths - Other than National Highways

Bridge Two Way One WayTwo Lane Single Lane Two Lane

Length AADT Shldr Lanes Shldr Width Shldr Lane Shldr Width Shldr Lanes Shldr WidthAny <100 1.0 6.0 1.0 8.0 0.6 3.0 0.6 4.2 - - -Any 100-500 1.0 6.0 1.0 8.0 2.0 3.0 1.0 6.0 - - -Any 500-1000 1.0 6.5 1.0 8.5 2.0 3.25 1.0 6.25 - - -<20 1000-2000 1.5 6.5 1.5 9.5 2.0 3.25 1.0 6.25 - - ->20 1000-2000 1.0 6.5 1.0 8.5 2.0 3.25 1.0 6.25 - - -<20 >2000 2.0 7.0 2.0 11.0 2.0 3.5 1.0 6.5 2.0 7.0 1.0 10.0>20 >2000 1.0 7.0 1.0 9.0 2.0 3.5 1.0 6.5 1.0 7.0 1.0 9.0

NOTES:1. Wherever possible, bridge carriageway widths should equal the approach carriageway widths.2. Use 3.0m shoulders adjacent to a barrier centreline marking or consider further widening to provide for auxiliary lane/s.3. Add appropriate lane widths to the two lane configurations to determine multi-lane bridge widths.4. All culverts are to be designed for full width of formation.5. AADT’s are within 20 years.6. If a bridge is part of cycle route and/or is in a built-up area, extra shoulder width will be required to allow adequate cyclist

access, and pedestrian facilities will be required.

Table 7.17 Bridge Carriageway Widths - National Highways

Bridge Two Way One WaySingle Lane Two Lane Single Lane Two Lane

Length AADT Shldr Lane Shldr Width Shldr Lanes Shldr Width Shldr Lane Shldr Width Shldr Lanes Shldr Width

<20 <3000(a) - - - - 1.5 7.0 1.5 10.0 2.0 3.5 1.0 6.5 - - - -

<20 >3000(a) - - - - 2.0 7.0 2.0 11.0 2.0 3.5 1.0 6.5 2.0 7.0 1.0 10.0

>20 <1000/ - - - - 0.6(b) 7.0 0.6(b) 8.2 2.0 3.5 1.0 6.5 - - - -lane

>20 >1000/ - - - - 1.2(b) 7.0 1.2(b) 9.4 2.0 3.5 1.0 6.5 2.0 7.0 1.0 10.0lane

NOTES:1. Wherever possible, bridge carriageway widths should equal the approach carriageway widths.2. Use 3.0m shoulders adjacent to a barrier centreline marking or consider further widening to provide for auxiliary lane/s.3. Add appropriate lane widths to the two lane configurations to determine multi-lane bridge widths.4. All culverts are to be designed for full width of formation.

(a) AADT within 10 years, other AADT’s are within 20 years.(b) Minimum allowable shoulder widths have been used.

5. If a bridge is part of cycle route and/or is in a built-up area, extra shoulder width will be required to allow adequate cyclistaccess, and pedestrian facilities will be required.

7.10.2 Pedestrian/Cyclist Bridges

The minimum vertical clearance to the undersideof pedestrian/cyclist bridges over traffic lanes andshoulders is 5.5 m where the bridge is protectedby other structures or more generally 5.7m.However, due to their lighter structure,consideration should be given to increasing thisclearance to 6.0m, particularly at isolated sites.The requirements of Table 7.21 must be applied.Vertical clearances over footpaths should not beless than 2.4 m and desirably 2.5 m. Clearanceover cycleways should not be less than 2.4m. If alower height is used, signs to warn users of thelow clearance should be installed.

Handrails on bicycle bridges are to be inaccordance with Chapter 5, Section 5.5.5.

The minimum clear width of a pedestrian bridgeshould be 1.8 m. This width is adequate for thepassage of up to 300 people per hour and allowstwo wheel chairs to pass.

For shared bicycle/pedestrian bridges, theminimum width is 3.0m. Where the volumes ofpedestrians and/or cyclists is high, the twofunctions should be segregated and theappropriate width for each function applied (seeAustroads, 1999).

Pedestrian and cyclist overpasses may need to befully enclosed to prevent objects being thrownfrom them on to the roadway below.

7.10.3 Lateral Clearance

(a) Road

The lateral clearance from the edge of thetravelled way to bridge piers, abutments, retainingwalls and other fixed objects should conform tothe requirements for clear zones (see Section 7.6).However, if the desirable clear zone cannot beachieved and it is not possible to remove theobject from the clear zone (see Section 7.6), theobject should be made frangible or protected bythe installation of a traffic barrier, with attentionbeing paid to the shy line effect and workingwidth (see Section 7.2.1). Refer Table 7.19 forlateral clearance to fixed objects.

In general, shop awnings are to be set back aminimum of 0.6m from the kerb face. Clearance toawnings and buildings should be in accordancewith the relevant Local Government requirements.

Signs and associated support structures should belocated in accordance with the MUTCD (Qld). Ingeneral, the sign face should be placed behind thekerb face by a minimum horizontal clearance of0.6m.

Table 7.19 Lateral Clearance to Fixed Objects

85th Percentile Clear Zone Shy Line WidthSpeed Width (m)(km/h) (m) Left Right

≤70 3.0-3.5 1.5 1.080 3.5-4.5 2.0 1.090 4.0-5.0 2.5 1.5

≥100 ≥4.5 3.0 2.0

Note: Clear zones vary according to traffic volume -must be assessed using Figure 7.12.

(b) Working Width

The working width is the lateral distance requiredfrom the face of a rigid barrier to an element (suchas bridge piers, walls etc.). See Figure 7.22.

Table 7.20 gives suggested working widthsappropriate for different speed zones.

A 4.3m high rigid and/or articulated vehicle wasused to determine the following working widthoffsets, relative to impact speed and crossfall forstandard height rigid barriers only.

Table 7.20 Working Widths

Speed Zone 0% x’fall 3% x’fall 7% x’fallHigh - 100km/h 0.8 0.9 1.1Low - 60km/h 0.5 0.6 0.8

As rigid barriers have no dynamic deflection, thevehicle inertia becomes an issue.

September 2004 7-59


7

7-60 September 2004

When considering vehicles with high centres ofgravity, the vehicle will pivot about the roll axis asshown in Figure 7.22.

Figure 7.22 Working Width

(c) Boundary

The clearance of the road elements (hinge point ofbatters) from the boundary of the road reserve hasto accommodate space for maintenance of theroad elements and frequently Public Utility Plant(e.g. Communications cables, Gas pipelines).Noise barriers and cycle ways are placed in thisspace where it is convenient.

The actual dimension of the clearance will dependon all of these factors (if known) as well as theability to acquire the necessary property. Thegeneral minimum for all roads is to be 10m, with15m adopted for motorways and major highways.The absolute minimum width at restricted sites is5m and this should be tolerated for short distancesonly - 5m provides for a maintenance vehicle totravel along the road boundary. In all cases, theminimum clearance to the edge of travelled way isto be the clear zone required, provided the clearzone is not to be used for pedestrian or cyclemovements - these movements are to be allowedfor outside the clear zone.

Note that it is not necessary to acquire additionalland for Public Utility Plant. These services arerequired to acquire their own land but may bepermitted to use available space provided theoperation of the road is not compromised. PublicUtilities are not generally permitted to occupyland on a motorway road reserve.

7.10.4 Vertical Clearance

Clearances are to be based on the ultimate crosssection using the method of measurement shown inFigure 7.23. Minimum vertical clearances requiredfor different road types are shown in Table 7.21.Consideration should be given to the use ofconvenient alternative routes (e.g. using the rampsof a diamond interchange) where a clearance of 6m or more is required thus allowing a lower (andpresumably cheaper) bridge to be built.

Table 7.21 Minimum Vertical Clearances

Description of Preferred Absoluteof Road Minimum Minimum

Very High Clearance 6.5m 6.0mRoutes (where no suitableconvenient alternative is available)

Highways and 6.0m* 5.5m*MotorwaysDeclared Roads 5.5m* 5.5m*Other Arterial and Main Roads 5.5m* 5.5m*Other Roads 5.3m* 4.8m**

* Heights provide 300 mm resurfacing or pavementstrengthening to the major road, and 100 mm to“Other Roads”.

** Legal height of livestock and vehicle carryingvehicles is 4.6m. Where it is likely that these types ofvehicles will use the road, the minimum clearancemust be 4.8m.

Signs are to be placed to provide a minimumvertical clearance of 2.0 m when installed onfootpaths and 5.5 m minimum for signs that arelocated over a traffic lane. For overhead PublicUtility Plant, see Section 7.10.7.


7

NOTES:1. Clear zone is speed related.2. Vertical clearance for pedestrians is 2.4m.3. Vertical clearance for cyclists is 2.5m.4. Awnings set back 0.6m from kerb face. For bus

stops, where the bus must access the stop at asteep angle, the clearance must be 0.8m. This 0.8mclearance must be provided to all objects in thevertical plane at these locations.

Figure 7.23 Roadway Clearances

7.10.5 Pedestrian/CyclistSubways

General

Pedestrian subways are not the preferred methodof providing for grade separated pedestriancrossings. They are not favoured by pedestriansand cyclists because of the potential danger posedby the “hidden” nature of the crossing. However,it is sometimes the case that a subway is the onlyreasonable alternative.

Subways should be lit and care taken with thedesign to ensure that “hiding” places do not occur.There should be a clear line of sight from one endto the other and this should preferably be availablefrom the adjacent street. Access should be bymeans of ramps or a combination of ramps andstairs provided that wheel chair access is fully

available. The access should be designed to caterfor the needs of sight-impaired people and thenecessary features to guide them incorporated.

Landscaping and services should be located so asnot to obscure sight lines. High quality, vandalproof lighting will be required in subways toenhance personal security. Murals can often beprovided to discourage graffiti.

Design should be in accordance with AS1428 andAustroads, 1995a and 1999.

Cross Section

The desirable interior cross section for subways is6.0m wide by 2.7m high (clear of light fittings,signs and other equipment). In constrainedsituations, a width of not less than 3.0m may beacceptable. The minimum clear height allowed is2.4m.

Walkway crossfall is to be not greater than 2.5%with 2.0% preferred to cater for impaired users.

Grades

Longitudinal grades in the subway should be notless than 0.3% in one direction to allow forlongitudinal drainage. The maximum grade in thesubway should not exceed 5%.

For access ramps, the maximum grade to beadopted is 1 on 14 with landings at intervals notexceeding 6.0m. Landings should be not less than1.5m x 1.5m in area.

7.10.6 Clearance to Railways

The relevant railway authority sets the clearancerequirements over railways. For Queensland Rail,their drawing No. 2231, included here as Figure7.24, gives the requirements for particularcircumstances. However, it is imperative that itis understood that this is to be used as a guideonly and actual clearance requirements at aparticular site must be determined inconsultation with Queensland Rail.

The actual clearance allowed will depend onspecific site parameters such as future trackrequirements, track geometry and overhead

September 2004 7-61


7

7-62 September 2004

electric traction geometry. In addition, a numberof design and construction issues will need to beaddressed. These include:

• Impact loads;

• Erection methods and procedures;

• Temporary clearances during construction; and

• Safe working on Railway property.

Other issues may have to be considered inaddition to these at a particular site.

As these issues can have a significant impact onthe whole design of the facility, it is imperativethat they be addressed at the concept stage of thedesign. Advice should be sought from theManager Civil Engineering, Queensland Rail, asearly as possible in the process.

7.10.7 Public Utility Plant

Clearances to overhead Public Utility Plantrequire special consideration. They vary fromutility to utility and for classes within a utility(e.g. electricity mains) depending on the specificfeature under the overhead service and thecharacteristics of that service.

The requirements of the Authority involvedshould be established at the Concept and Planningstages of a project development. Table 7.22 isprovided as a guide to the clearances to beexpected.

Horizontal allocation of space for undergroundservices is described in Section 7.5.2.

7.11 Special Considerations

7.11.1 Roads on Expansive Soilsin Western Queensland

In order to obtain best performance, it is importantto take advantage of the low average rainfall andnormally short rainfall durations of the westernareas. The relatively low traffic volumes also helpto lessen impacts on the road performance. All

design, construction and maintenance activitiesshould give priority to keeping moisture out of theroadway rather than assuming it will enter andproviding measures to remove it. This principle isdifferent from that usually adopted for wet areasand it is important to distinguish the difference.

Some moisture will of course enter the roadway,but the amount and its effect can be minimisedand kept clear of the wheel path locations. This isachieved by a combination of:

• moisture control;

• pavement material properties;

• type cross section.

This section deals with the type cross section only.

Figure 7.25 illustrates an unacceptable situationfor design through expansive soil areas.

Figure 7.26 illustrates the desirable type crosssection features outlined in the followingdiscussion.

Shoulder Protection

Even with the best low permeability/adequatestrength paving materials, moisture will still enterthe roadway and produce edge effects ofpavement and subgrade weakening to about onemetre in width. Best performance will be achievedby providing at least one metre of sealedpavement outside the edge of the wheelpath. Thewheelpath position should be determined fromobservations taken of at least 100 heavy vehicleson roads of similar traffic volume andcomposition, type cross section and alignment.Consideration of any different edge and centreline marking is required. Additional lane widthmay be required on crests and curves to allow fordifferent wheelpath positions due to visibilityrestrictions and vehicle tracking characteristics.

Encased Pavements

When the traffic lanes and shoulders are fullysealed, moisture can still be absorbed bypavement material exposed on the batters. Largeexposed areas will create problems even with lowpermeability materials. Situations to avoid


7

include excess pavement width beyond the seal,loose pavement spilled or graded down the battersand very flat pavement batters. These can beovercome by cutting the pavement batter to 1 on 2at the seal edge, removing excess pavementmaterial and encasing the pavement withembankment at a 1 on 4 slope. Good compactionat the pavement edge is important to minimisemoisture entry.

Even more positive encasement can be providedby adding 300 to 500mm of embankment on bothsides of the formation. Spraying bitumen (withoutcover aggregate) on the top 300mm of thepavement batter before encasing would furtherimprove performance, particularly in the first fewyears.

Road sections constructed initially or throughsubsequent maintenance with encased pavementshave been found to have substantially less edgeheave and roughness increase rates. This isattributed to reduced moisture infiltration andevaporation and the greater uniformity obtained.

Pavement Depth

Thin pavements have been shown throughcomputer simulation and monitoring ofinstrumented pavement sites to absorb lessmoisture than thicker pavements. With theresultant stronger subgrade and more appropriatetraffic loading distribution assessments, thesepavements can carry much more traffic than thecurrent pavement design procedures attributed tothem.

Pavements as thin as 100mm have been used butare not recommended because of constructiontolerances, compaction difficulties and the riskfrom severe damage from heavily overloadedvehicles. However, many pavements of 250mmand even 150 and 200mm have performed well.There appears to be no advantage in using depthsgreater than 250 to 300mm.

In addition to the above advantages, a singlepavement course (or at most two courses) willconserve material resources, save costs, reducelongitudinal crack widths and shortenconstruction time. The latter will provide otherbenefits in decreasing exposure to excess rainfall.

The current pavement depth design process doesnot appear to replicate the observed roadperformance. Further development is needed toprovide an improved pavement design process.However, issues other than depth are important.

Sealed Pavement Batters

Sealed pavement batters have been used on anumber of jobs in conjunction with verypermeable base materials. They reduce theseverity of moisture entry but will not eliminate it.The more uniform conditions created will reduceroughness increase rates and extend pavementlife. Disadvantages include increased constructionand reseal costs, and damage from traffic andmaintenance operations. Their use as a long termmeasure is not recommended universally, but theyhave a possible use as a corrective treatment onexisting permeable pavements.

Batter Slope and Formation Height

Flat embankment batters and low formation heightsshould be used whenever possible as these willminimise moisture changes below the pavement.

Batter slopes of 1 on 4 or flatter should be used onall fills up to 2m. The formation needs to be apositive height above the surrounding terrain butkept as low as possible (say 300 - 500mm at thetop of pavement at formation edge).

Longitudinal Drainage

In flat country, table drains should never beconstructed as they will hold water for extendedperiods and adversely affect road performance.Where existing table drains occur they should befilled with embankment. In addition, flatterbatters can be used to keep any ponded waterfurther away from the road. Diversion drains tonearby borrow pits can also help.

On gentle grades, table drains may be used tominimise earthworks where positive drainageoccurs, provided erosion is not an issue. Theyshould be used in cuttings but long shallowcuttings should be avoided particularly wheregrades are nearly flat. A table drain depth of300mm is suggested with flat bottom drains usedif excessive siltation is a problem.

September 2004 7-63


7

7-64 September 2004


7

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33

Table 7.22 Minimum Overhead Clearance to Various Utilities

September 2004 7-65


7

Figure 7.24 Required Clearances for Proposed Structures

7-66 September 2004


7Thick permeablepavement

Overwidth pavement orunsealed shoulder

Exposed pavement batter withloose surface on a flat slope

Loose excess pavementmaterial

Water ponded in tabledrain

Figure 7.25 Unacceptable Features (Expansive Soil)

CL

H

CL

Traffic lane widths to suit vehicle

numbers and composition. Additional

width on crests and curves as required.

Formation height 0.3-0.5m wherever posible.

Single lane road to be widened to twolanes where visibility is limited.

2.

NOTES: 1.

3.

##

#

#

Shoulder protection 1.0

Bitumen seal

(Refer note 3.)

(Refer note 1.)

(Refer note 2.)

Traffic lane-4.0

B. SINGLE LANE ROAD

0.3

#

Excess pavement trimmed

back to a 1 on 2 slope

and encased with

embankment

0.5

1 on 4or flatter

Wheelpathwander

A. 2 LANE ROAD

ALTERNATIVE

(FOR BETTER

ENCASEMENT)

No table drains

in flat country

Traffic lanes-6.0,6.5 or 7.0m

Bitumen seal

1 on 4or flatter

3%3%

Thin lowpermeabilitypavement

1 on 4

1 on 2

Table drains to havepositive drainage.

Provide flat bottom

Avoid long

shallow cuttings

(preferred)

Figure 7.26 Desirable Type Cross Sections (Expansive Soils)

Zonal Use of Expansive Materials

The zonal use of expansive materials to place themin the embankment beyond the influence ofseasonal effects has application in higher rainfallareas (Technical Note No.10 “Expansive ClayEmbankments”). It is not considered practical ornecessary in western areas if the recommendationsof this technical note are followed.

Permeable materials should never be used asembankment or a selected layer over expansivesoils as the increased moisture entry will morethan offset any advantages of an improvedsubgrade.

Use of Existing Formation

Construction on the line of an existing formationcan be an advantage, provided sufficientformation height is achieved, as it is liable toprovide moisture conditions close to equilibrium.However, good performance has also beenachieved on sections of new alignment. The issuesdiscussed in this section, together with moisturecontrol and selection of pavement materials areconsidered to have a greater influence onperformance.

Construction costs and all other relevant factorsmust be considered when deciding whether toconstruct on the existing alignment.

Table 7.23 provides a check list summarising thecross section design issues.

7.11.2 Roads in Rainforest(including Wet Tropics)

Carriageway Widths

The width of the road should generally be basedon the traffic volume, the type of road beingdesigned, the speed of the traffic and the likelyenvironmental impacts. (See 7.2, 7.3, 7.4 and 7.5.)

Other factors to consider include the following.

Providing carriageway widening on curves forlarger vehicles is necessary. Adopting theminimum radius curves in steep terrain may resultin the need to provide extensive widening for Bdoubles and for sight distance. For instance on a50m radius curve a B double would require thetraffic lane to be widened to 6m.

A verge width may also need to be allowed toprovide for guard rail, verge drains and vergeberms on fill.

September 2004 7-67


7

Feature DetailsWheel Path Positions • Determine OWP position for similar road, traffic volume and composition,

type cross section and alignmentShoulder Protection • Provide 1m min sealed shoulder protection outside edge of OWPCrests and Curves • Adjust widths on crests and curves if appropriateEncased Pavement • Provide fully encased pavement with no exposed surfacesPavement Depth • Provide thinnest pavement that will carry the trafficBatter Slope • Keep batters 1 on 4 or flatter (up to 2m high)Formation Height • Keep formation edge height 300 to 500mm at top of pavement wherever

possibleTable Drains • Avoid table drains in flat country

• Provide 300mm deep table drains where positive drainage is available• Avoid pondage of water within 5m of the formation for extended periods• Provide flat bottom table drain if excessive siltation is a problem

Permeable Embankment • Don’t allow the use of permeable materialsExisting Formation • Consider alignment options which include reuse of any existing formation

Table 7.23 Checklist for Cross Sections on Expansive Clays (not for floodways, perched water tables orclose to ponded water)

7-68 September 2004

The single most important way to minimiseimpacts of roads through tropical rainforest is byreducing clearing width for as much of the roadlength as possible. Planning should thereforeidentify mechanisms to reduce clearing width asfar as possible (such as use of barriers rather thanrelying on clearing for the necessary recoverywidth).

On scenic (tourist) 4WD roads or in WorldHeritage Areas where one lane is desirable (takinginto account safety considerations), width can bereduced by providing drainage on one side only(crown shape has drainage each side).

On new two-lane roads, it will rarely be possibleto achieve canopy closure. Alternative ways ofproviding connectivity will be required.

For high volume roads requiring four lanes ormore, dual carriageways will be required. Fourlane (or more) undivided two-way roads are notacceptable for traffic safety reasons. In thesecases, a dual carriageway, which enables retentionof natural vegetation in a wide median mayprovide greater opportunity for fauna crossing theroad. Fauna then only has to contend with trafficfrom one direction over a shorter distance.However, it is preferable to provideinterconnectivity with short tunnels and longbridges at suitable locations.

The typical cross-section adopted for the roadcorridor will impact on the environment in avariety of ways and may need to be varied alonga route to minimise a particular impact. Generally,for two lane roads the minimum clearing widthswill produce the least impact.

The cross section of roads through natural habitatwill need to be determined based on theconservation values requiring protection.

On local access tourist roads two single lanesseparated by a wider median may also have lessimpact than the two lane road.

Importantly, the overall width of the disturbedroad corridor is an issue requiring consideration.In general, minimising the overall width fromcleared forest edge to cleared forest edge willreduce the impact.

In addition to clearing width, selection of crosssections should consider the potential impacts ofside cuts and batters, as in many circumstancesthey become fauna barriers, in effect impassablecliffs.

Table 7.24 provides some of the advantages anddisadvantages of the different carriageway typesand suggests areas where they may be used.

It is important to note that best practice willinvolve the consideration of different crosssections over relatively short sections. As anexample, for environmental reasons divided twolane carriageway may only need to be over a shortdistance to maintain connectivity of a particularhabitat (eg. a riparian gallery rainforest, or asteeper gully).

Road Formation/Earthworks

The desired outcome is to minimise earthworksand disturbance. An essential first step is tointegrate the design with the site and the designselected should be compatible with the naturalcharacteristics of the area (geological, soil,landform and hydrological limitations).

By designing roads which minimise the area to becleared, the height and slope of batters and thevolume of earthworks, the resultant roadalignment will generally be a safe, cost effectiveand an environmentally sound project thatrequires minimal ongoing maintenance.

Batters should be designed to a stable slope basedon consideration of topography, soil type,vegetation and rock formations for revegetation.Note, this must also consider needs to minimiseerosion. Narrower total widths may be achievedby appropriate use of gabions, crib walls and rock.

Consider rounding of batters and using constantbatter line in less sensitive areas to provide a morenatural cut/fill batter. The constant batter offsetalso better blends the earthworks into the terrain.

On cuts, it is as important to ensure long termstability as it is to minimise constructiondisturbance. A steep cut which fails and collapseswill result in more disturbance and environmentalimpacts over time than a wider, less steep cut


7

September 2004 7-69


7

Cross Section Type Advantages Disadvantagesand Suitability

Unsealed road Cheaper construction costs. As traffic volumes increase,Suitable for low volume roads with maintenance costs increase moderate grades. significantly along with erosion and

sedimentation.In some circumstances provides Steep grades more readily eroded andpresentation opportunity and may require sealing.“character”. May need to close to traffic during the

wet season.

Single lane sealed road Requires minimum width of disturbance. Requires widening at crests and curvestwo way Cheaper solution than a 2 lane sealed for safety.

road. Unsuitable for high volume roads.Suitable for low volume If in closed forest and narrow clearing, Unsealed verges may erode.access roads only. may enable canopy connectivity to be

maintained.

Two lane carriageway, Requires minimum width for clearing. May be a safety concern with wrongeach way separated by way movements.a wide median Enables canopy connectivity to beSuitable for low volume maintained. Need to provide areas for passingroads especially access disabled/parked cars (only on uphillroads and tourist roads. Enables refuge area within the median side).Note: this option has not for animals (whilst crossing).been used in the wet With long lengths and medium traffictropics region, most likely In steep sidelong country this design volumes overtaking opportunitiesapplication is for short will better match the terrain with less may need to be provided.distances to meet specific height to cuts and fills.environmental requirements.

Two lane, two way road Provide for some canopy connectivity For higher volume roads may requireif minimum widths adopted. passing lanes.

This is the normal road Generally less total width of As widths increase with traffic volumescross section for rural roads disturbance than two single canopy connectivity will be more and is likely to be the usual carriageways. difficult to maintain.solution in most cases. Cheaper to construct than two single Less gaps in the traffic stream than a

lane carriageways. divided carriageway.

Four lane divided Provides high capacity and overtaking Likely to be more expensive than a fournarrow median opportunities. lane undivided facility.(New Jersey barrier)May be an option where Provides increased safety and New Jersey barrier will prevent fauna increased capacity and eliminates head on collisions. crossings across the road although if safety is required on traffic volumes require a four lanesteep hilly sections and facility it is unlikely that sufficient gaps the terrain precludes in the traffic stream will occur to enable construction of a second animals to cross safely.carriageway.

Four lane divided wide Breaks the total width into two parts May have a higher construction cost median enabling some canopy connectivity to than a four lane undivided facility.

be maintained.May be the preferred Total width of disturbance likely to be solution in environmentally Breaks the traffic stream into two greater.sensitive areas where the streams producing larger gaps formedian is forested. fauna to cross, however grade separated

fauna crossings are the preferred solution.In steep sidelong country this will bettermatch the terrain.Provides safer overtaking opportunities.Prevents head on collisions.

Table 7.24 Cross Section Suitability

7-70 September 2004

which (although it has a greater area ofdisturbance during construction) is revegetatedwith surrounding vegetation species and regainsits habitat values.

The design of the batters should be coordinatedwith the environmental protection measures andthe landscaping design. Revegetating steep battersis difficult and expensive and it may be better totolerate some additional disturbance in the shortterm to achieve better revegetation in the longterm.

Cut and fill can have a major visual impact. Thearea exposed during earthwork operations alsocan lead to erosion and sedimentation ofwatercourses.

The cut and fill can dominate the landscape and itis desirable to minimise the earthworks as far aspracticable.

The cut and fill transition zones should bedesigned so that they do not obstruct escaperoutes for any fauna.

The distant view of the road alignment should beassessed and if major cuttings or fills will bevisible then consideration may need to be given toaltering the alignment to avoid the cut beingviewed from distant vantage points. Where the cutand fill cannot be avoided then revegetation of thebatter should be given a high priority.

Various revegetation techniques are available fromhydraulic seeding and mulching to planting withviro cells and spraying of freshly exposed rock withan activator that promotes moss and algae growth.

Water running over steep batters will develop ahigh velocity and resulting erosion of anyunprotected batter. Prevention of runoff waterrunning over batters is essential to prevent erosion.

Consider the use of gabions or other retainingdevices in steep sidelong country (especially insensitive rainforest areas).

Incorporate surface relief on batter faces in thedesign to provide far greater microhabitat. Thiscan be achieved by roughening cut slopes toprovide horizontal steps along the batter or evensmall (300 mm) benching to enable topsoil to be

retained and assist revegetation. (See Figures 7.17and 7.18.) Contour ripping and top soiling shouldbe used where possible.

The existing rainforest topsoil and humus shouldbe retained and respread on batters in the locationsfrom which it was stripped.

Topsoil should not be transported from other areasdue to the possibility of importing exotic weedsand/or plant pathogens.

Note that in the Wet Tropics World HeritageArea, apart from the cut and fill associatedwith the earthworks, obtaining additionalmaterial from borrow pits is prohibited unlessspecific approval has been obtained from theWet Tropics Management Authority. Dumpingmaterial over the edge of batters is prohibited.

Surface runoff damaging cut and fill batters shouldbe prevented. Catch drains, diversions banks andchannels above and below batters, and bencheswithin them, will intercept surface runoff andconduct it to safe disposal points. This will reducethe hazard of sheet erosion and batter slumps.

Berms or benches are recommended on batterswith a vertical height greater than 5 metres. Thebench should be at least 1 metre wide, butadditional width may be necessary to allow for themovement of equipment used to establish andmaintain vegetation on the batters. However, thismay be avoided by progressively revegetating thecut (hydraulic seeding and mulching) at the levelof each bench as the cut is excavated to avoid theneed for wide benches. If the batter is relativelysteep (and it is unlikely to grow trees) a bench of2-3m may allow trees to be established, this willeffectively stabilise and screen the batter. (Seealso Section 7.8.4.)

Benches should also be considered for battersover 3m high to facilitate planting.

Benches should have a maximum longitudinalgrade of 1% if vegetated or 0.5% if paved. Themaximum grades should be restricted to a levelconsistent with the maximum permissible velocityfor the type of lining used. A maximum crossslope of 10% (1 on 10) on the bench towards thetoe of the upper batter should apply.


7

With cut batters, a catch drain or diversion bank(preferred) should be constructed above the top ofthe cut before excavation commences. Temporarytoe drainage should be maintained as the workprogresses, with permanent toe drainage installedwhen the final depth is reached. To preventerosion, a catch drain will require concrete lining.

For fill batters, permanent toe drainage should beinstalled prior to construction and shoulddischarge via a sediment basin to a suitable outlet.At the completion of each work period during theconstruction of the bank, or at the onset of rain, awindrow of suitably compacted soil materialshould be constructed along the recentlycompleted fill slope.

Early stabilisation of exposed batters is essential.They should be adequately protected from erosionby vegetation, or other means, within 4 days oftheir construction. Best practice is to revegetateall exposed areas immediately.

In summary, the following principles of erosionand sediment control should be incorporated inthe design:

• Integrate the project with the site;

• Plan and integrate erosion control withconstruction activities;

• Minimise the extent and duration ofdisturbance;

• Control stormwater flows onto, through andfrom the site;

• Use erosion control measures to prevent on-sitedamage;

• Use sediment control measures to prevent off-site damage;

• Stabilise disturbed areas quickly;

• Inspect and maintain erosion and sedimentcontrol measures.

(For more detailed discussion, refer toConstruction Site Erosion and Sediment Control -Course Notes and Field Guide - References andOther Reading.)

Creeks and streams are the principal corridors forfauna movement in rainforest areas. Therefore theroad must be high enough above the stream toenable suitable fauna crossings to be installed inculverts or under bridges (see Chapter 3). Culvertsrequiring a concrete base should not be used inpermanently flowing streams - they cannot beconstructed without causing major streamdisturbance.

The cut/fill transition zone provides areas forfauna crossings and barriers across these sectionsshould be avoided.

Consider using temporary retaining structures onfill (downhill slopes) to prevent downslopecontamination by spoil.

7.12 Typical Cross Sections

The following pages show typical cross sectionswhich may be used as guides for design, althoughmodifications may be needed to meet therequirements of each particular site.

• Figure 7.27 Two Lane Two Way Rural Road

• Figure 7.28 Multi Lane Rural Road

• Figure 7.29 Undivided Urban Road

• Figure 7.30 Multi Lane Urban Road

• Figure 7.31 Alternative Urban Arterial RoadTreatments

• Figure 7.32 Motorway Cross Section Elements

Note that these figures are not necessarily drawnto scale.

For routes accommodating multicombinationvehicles (MCV), allowance has to be made for thesize of the vehicles and their trackingcharactristics. Appendix B sets out the minimumcarriageway clearance widths for these routes.Table B1 should be used in conjunction with thefollowing cross sections. The lane widthsindicated in the table and the following figures donot include allowance for curve widening. Wherenecessary, curve widening should be appliedaccording to Chapter 11, Section 11.10 “CurveWidening”.

September 2004 7-71


7

7-72 September 2004


7

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Figure 7.27 Typical Cross Section of Two Lane Two Way Rural Road

September 2004 7-73


7

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7-74 September 2004


7

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September 2004 7-75


7

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7-76 September 2004


7

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Figure 7.31(a) Typical Cross Section of Urban Arterial Road - Mixed Function Type

September 2004 7-77


7

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Figure 7.31(b) Typical Cross Section of Urban Arterial Road - Separated Function Type

7-78 September 2004


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September 2004 7-79


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7-80 September 2004

References

American Association of State Highway andTransportation Officials (AASHTO), 2002:“Roadside Design Guide”.

Australian Road Research Board (ARRB), 1983:“Guidelines for Rural Road Improvements - aSimulation Study” ARRB IR AIR 359-10.

Austroads, 1987: “Standards and Guidelines forthe Construction of National Highways”.

Austroads, 1993: “Guide to Geometric Design ofRural Roads”.

Austroads, 1995a: “Guide to Traffic EngineeringPractice”, Part 13 - Pedestrians.

Austroads, 1995b: “Guide to Traffic EngineeringPractice”, Part 11 - Parking.

Austroads, 1999: “Guide to Traffic EngineeringPractice”, Part 14 - Bicycles.

Department of Main Roads QLD, 1997: “Manualof Uniform Traffic Control Devices - Guide toPavement Markings”.

Department of Transport and Communications,Federal Office of Road Safety, 1991: “AustralianCode for the Transport of Explosives by Road andRail (Australian Explosives Code)”.

Department of Transport and Communications,Federal Office of Road Safety, 1992: “AustralianDangerous Goods Code”.

NAASRA, 1986: “Guide to the Design of RoadSurface Drainage”.

NAASRA, 1979: “Guide to the Provision andSignposting of Tourist Facilities”.

NSW Department of Land and WaterConservation, Soil Conservation Service, 1998:“Construction Site Erosion and Sediment Control- Course Notes - Level 2”.

NSW Department of Land and WaterConservation, 1996: “Urban Erosion andSediment Control - Field Guide”.

PIARC, 1999: “The Quality of Road Service -Evaluation, Perception and Response Behaviourof Road Users”.

PPK Environment & Infrastructure Pty Ltd, 2000:Brisbane HOV Arterial Roads Study Final Report- Queensland Department of Main Roads,Queensland Transport and Brisbane City Council.

Queensland Department of Main Roads, 1975:“Urban Road Design, Volume 1”.

Queensland Department of Main Roads, 1998:“Road Landscape Manual”.

Queensland Department of Main Roads, 2000a:“Fauna Sensitive Road Design, Volume 1: Pastand Existing Practices”.

Queensland Department of Main Roads, 2000b:“Road Traffic Noise Management: Code ofPractice”.

Queensland Department of Main Roads, 2001:“Road Drainage Design Manual”.

Queensland Department of Main Roads, “RoadDesign Manual, Volume 1”.

Roads and Traffic Authority (NSW): “RoadDesign Guide”.

Standards Australia, 1990a: “AS1742.6 - Manualof Uniform Traffic Control Devices - Service andTourist Signs for Motorists”.

Standards Australia, 1990b: “AS1742.8 - Manualof Uniform Traffic Control Devices - Freeways”.

Standards Australia, 1992: “AS1743 - Road Signs- Specifications”.

Standards Australia, 1993: “AS1742.7 - Manualof Uniform Traffic Control Devices - RailwayCrossings”.

Transportation Research Board, Washington DC(TRB), 1994: “Highway Capacity Manual”Special Report 209.

Wilden, L.A., 1997: High Occupancy VehicleFacilities Policy and ImplementationConsiderations - Queensland Main Roads SouthEast Region Symposium.


7

Relationship to OtherChapters

• Chapter 1 deals with the strategic requirementsof the road system and will have a significantinfluence on the type of cross section adopted;

• Chapter 2 describes the planning of roads – theappropriate cross sections for these roads willhave a significant effect on the planningoutcomes;

• Chapter 3 sets out environmental requirements– these are crucial in the design of crosssections;

• Chapter 4 describes the standards to be appliedto roads of different types;

• Chapter 5 describes the particular requirementsof various road users –

- Pedestrians;

- Cyclists;

- Road users with a disability; and

- Motorcyclists; plus

• Chapter 5 defines the dimensions of the variousdesign vehicles;

• Operating speed can be affected by the crosssection (Chapter 6);

• Chapter 8 is closely related to this chapter andthey must be read in conjunction with eachother;

• Sight distance on horizontal curves will affectthe cross section (Chapter 9);

• The appearance of a road is affected by thedetail of the cross section (Chapter 10);

• Curve widening will affect the cross section(Chapter 11);

• Width of pavement is affected by the radius ofcrest vertical curves where manoeuvre sightdistance is the best available (Chapter 12);

• Intersection elements have dimensionsdependent on cross section requirements(Chapters 13 and 14);

• Widths of auxiliary lanes affect the crosssection (Chapter 15);

• Interchange elements have dimensionsdependent on cross section requirements(Chapter 16);

• Providing for lighting affects the cross section(Chapter 17);

• Traffic signals require space in the cross section(Chapter 18);

• Providing for ITS is an integral part of the crosssection (Chapter 19);

• Cross section elements have to be applied to thedesign of roadside amenities (Chapter 20);

• The road cross section has to be compatiblewith railway level crossings (Chapter 21); and

• Bridges, retaining walls and tunnels have to bedesigned to the requirements of the crosssection required to serve the traffic carried(Chapter 22).

This shows that there is no aspect of road designthat is not affected by the cross sectionrequirements. There is an interrelationshipbetween the cross section elements and the otherdesign considerations and all design involvessome level of iteration between theseconsiderations and the cross section.

September 2004 7-81


7

7-82 September 2004


7

FrontOverhang

1070Wheelbase 3380

RearOverhang

1600

FrontClearance

CentreClearance

RearClearance

Normal

Front dive (braking)

Rear jounce

Full jounce

280

180

300

200

100

65

65

25

270

300

160

190

Clearance dimensions under various conditions for composite longest vehicle

Clearance dimensions under various conditions for composite shortest vehicle

Normal

Front dive (braking)

Rear jounce

Full jounce

150

85

160

100

125

100

100

75

115

135

45

65

FrontO.H560

Wheelbase 2030

RearO.H815

FrontClearance

CentreClearance

RearClearance

* Use normal load as a basis for design of entrances, but the effects of greater springdeflections should be checked.

* The dimensions shown relate to those of a composite design vehicle and do notnecessarily apply to the particular models shown.

Appendix 7A: Template for Vehicle Clearance at PropertyEntrances

Appendix 7B:Multi-Combination Vehiclesin Urban Areas

There are a number of clearance requirements tobe considered for MCVs travelling in urban areas.The carriageway widths should take into accountvarious existing features including parkingdemand, angle of parking and the demand for on-road cycling provisions.

The route should be further evaluated if theminimum carriageway width in the urban area isless than the applicable width shown in Table B1.

Through lanes provide travel without obstructiondue to parked vehicles or stationary turningqueues and therefore minimise the necessity forlane changing manoeuvres. It is preferable that atleast two continuous through lanes are availablein the direction of travel. Short sections of singlethrough lane may be permitted.

September 2004 7-83


7Table B1 Minimum Carriageway Clearance Widths in Urban Areas

B-Double Type 1 Type 2Feature Road Train Road Train

60-70 80-100 60-70 80-100 60-70 80-100km/h* km/h* km/h* km/h* km/h* km/h*

(Undivided carriageway - 2-way) Width 3.8 4.2 4.0 4.4 4.2 4.8between road edge and road centre

• with marked separation line 4.1 4.8 4.3 5.0 4.5 5.4• with in-road cyclists 5.3 6.3 5.5 6.5 5.7 6.9• with regular parallel parking 6.0 6.4 6.2 6.6 6.4 7.0• with regular angle (45°) parking 9.8 9.9 10.0 10.1 10.2 10.5

(Divided carriageway - single lane) 4.1 4.8 4.3 5.0 4.5 5.4Width between road edge and edgeof median/traffic island• with in-road cyclists 5.3 6.3 5.5 6.5 5.7 6.9• with regular parallel parking 6.3 6.4 6.5 6.6 6.7 7.0• with regular angle (45°) parking 9.8 9.9 10.0 10.1 10.2 10.5

(Divided carriageway - 2 lanes) 7.2 8.3 7.4 8.5 7.6 8.9Width between road edge and edgeof median/traffic island• with in-road cyclists 8.4 8.8 8.6 10.0 8.8 10.4• with regular parallel parking 9.4 9.9 9.6 10.1 9.8 10.5

(Divided carriageway - 3 lanes) 10.1 10.7 10.5 11.1 10.9 11.9Width between road edge and edgeof median/traffic island• with in-road cyclists 11.3 12.2 11.7 12.6 12.1 13.4

* Legal Speed Limit for the particular section of road being assessed.(Source: Assessing the suitability of routes for Multi-Combination Vehicles Guidelines, WA, 22 March 2000, p.6)

Documents

Cross Section - Department of Transport and Main Roads