BARRIERS BETWEEN ROAD AND RAIL: BARRIER … · BARRIERS BETWEEN ROAD AND RAIL: BARRIER ADJACENT TO RAIL EXPLAINED Page 1 of 17 BARRIERS BETWEEN ROAD AND RAIL: BARRIER ADJACENT TO

BARRIERS BETWEEN ROAD AND RAIL: BARRIER ADJACENT TO RAIL EXPLAINED

Page 1 of 17 BARRIERS BETWEEN ROAD AND RAIL: BARRIER ADJACENT TO RAIL EXPLAINED (BARLOW)

Susan Barlow, Queensland Main Roads

Dr Ross Pritchard, Queensland Main Roads

Arthur Theodoropoulos, Queensland Rail

Dr Rod Troutbeck, Troutbeck and Associates

SYNOPSIS The current standards for road and bridge barriers AS 3845 and AS 5100 assume the main risk of an errant vehicle is to the occupants of the vehicle. In the majority of cases, this is a valid assumption. However, when a rail corridor is parallel to or crosses the road corridor, the risk profile changes. If an errant vehicle crosses the path of a high speed commuter train, the risk profile resulting from the possible death or injury to hundreds of commuters means that a different approach is required to road and bridge barriers to reduce the likelihood of such an event. This paper presents the rationale for developing a risk matrix and a sensible interaction when road and rail corridors are in close proximity. It also outlines a design method for road and bridge barriers related to vehicle type, vehicle weight, road and rail status, effective height, performance levels and site environment. The method was based on a single risk management analysis for both bridge and road barriers.

INTRODUCTION The Queensland Department of Main Roads (QMR) manages the state controlled road network, which comprises approximately 34,000 kilometres of road. Queensland Rail (QR Network) manages a 10,000 kilometre rail network including coal, bulk freight, and passenger lines. This paper has been jointly prepared by QMR and QR Network. It outlines the background, method and application of the guidelines produced to advise engineers and designers on the road safety barrier requirements at the road and rail interface. Road/rail interfaces at level crossings have been excluded from this analysis. BACKGROUND With an increasing population growth in Australian cities, a number of new transport corridors are now being planned, developed and constructed. Increasingly, these transport corridors incorporate both a motorway and railway running parallel to each other, sometimes in close proximity and involving grade-separated interchanges often with road bridges crossing over the railway. An intrusion into the railway corridor by an errant vehicle, loss of cargo onto the rail track or debris resulting from the event can cause a major incident and lead to extensive disruptions to railway and road operations. A major incident could cause:


� Significant loss of life to rail passengers and the occupant(s) of the road vehicle(s),

� Damage to infrastructure, � Track blockage, � Damage to vehicles and trains, � Derailed train being hit by a train on adjacent tracks. or � Delays due to time taken for debris removal. In light of the increasing potential of incidents in shared corridors, work was initiated to develop a guideline for the road and bridge safety barrier requirements between road and rail corridors and interfaces. Queensland Main Roads and Queensland Rail collaborated to produce this guideline with the input of an independent expert on road safety barriers and risk management. RISK PROFILES There was a significant difficulty to overcome when negotiating agreement on the contents of the guideline, as the risk profiles for railway authorities are notably different to road authorities. The major differences are: � The public accept (albeit perhaps subconsciously or tacitly) that some fatalities

will occur on the road network' � Rail operators work in a “no accident” or “Zero Harm” environment' � Rail systems have fewer responsible people and fewer contributory factors when

an incident occurs compared with road crashes. Road crashes involve varying combinations of driver(s) error or impairment, suboptimal road design and/or vehicle malfunction, all of which have different system owners. In rail systems, there is a public perception that there is one system owner.

� Head-on collisions between road vehicles, even high occupancy vehicles such as buses, potentially have a lower severity outcome, in comparison to a crash involving a passenger train,

� Even give the previous point, crashes that involve transport modes that have many passengers not in control of the vehicle (e.g. coaches, trains and aircraft) have a tacit perception of greater risk and therefore greater onus of responsibility on the operators of those modes (e.g. air traffic controllers, train and bus drivers, etc.) than domestic motor vehicles1,

� High-speed commuter trains carry hundreds of passengers and the consequences of a crash involving high-speed commuter trains are severe. Crashes must be avoided,

� In the event of a rail crash, there is limited redundancy in rail operations for the diversion of trains following an incident and this can lead to severe delays across large sections of the network for extended periods,

� Trains need an obstacle free environment as they can not swerve, and � Trains have long breaking distances The key outcome of the investigation was to define the combined risk profile of a road corridor and a rail corridor in close proximity. The designer must address the combined risk profile of the road and rail corridor environment. Hence, the adoption

1 Refer to Australian Standard AS 4360 (2004) “Risk Management”.


of the risk profile of the rail authority which is to target “zero harm” to users and operating staff. An example of the possible consequences of a road/rail interaction was the 2001 Selby rail crash in the UK. This resulted in 10 fatalities and more than 70 injuries when an errant vehicle left the M62 motorway, coming to rest on the East Coast Main Line and caused the derailment of two trains. There was no road safety barrier where the vehicle left the motorway. (BBC News 2) QUEENSLAND CRASH ANALYSIS An analysis of single vehicle “run-off-road” crashes on Queensland roads was undertaken at the start of the project. This included instances where vehicles left the road on both the nearside and offside. In summary, for the five-year period, October 2002 to September 2007, there were: � 3 incidents where a train struck a vehicle (other than at a railway level crossing). � 25 incidents involving vehicles intruding into the rail corridor (other than at a

railway level crossing) Of the 28 "rail safety" incidences, the following vehicles were involved: � 17 cars (60.7%) � 5 trucks (17.9 %) � 3 articulated vehicles (10.7%) � 1 involving machinery (3.6%) � 2 unknown (7.1 %) Overall, the number of run-off-road crashes that occurred in Queensland are summarised below in Table 1.

Year Fatal Hospitalisation Medical Treatment

Minor Injury

Property Damage Only

Total

2002 22 249 168 89 397 925 2003 83 890 643 382 1638 3636

2004 84 966 668 410 1845 3973 2005 97 1056 719 429 1970 4271

2006 106 1039 731 451 1894 4221 2007 87 583 333 228 839 2070

Totals 479 4783 3262 1989 8583 19096

Table 1. Count of run-off-road crashes by crash severity and year

It follows from the data in Table 1 that the run-off-road incidences involving railways (not at level crossings), as a percentage of all run-off-road crashes, are 0.15%. Although this percentage is small and vehicles leaving the road and reaching a railway are infrequent events, a high severity consequence resulting from an incident could have very serious consequences. Therefore this warrants considerations to eliminate or minimise the risk. NATIONAL AND INTERNATIONAL PRACTICE REVIEW Initially a review of Australian practice and an international literature review was undertaken to obtain an understanding of current practice. At the same time, a

2 British Broadcasting Corporation News 2003 “In Depth: Selby Rail Crash” BBC News website


review of the relevant Australian Standards and Austroads “Guide to Road Design” was carried out. AUSTRALIAN ROAD AUTHORITIES When conducting research for the guideline, representatives from other state road authorities were consulted to determine what methods they used to determine the road’s safety barrier requirements at the rail and road interface. These road authorities included the Road and Traffic Authority (New South Wales), VicRoads (Victoria), Main Roads Western Australia and the Department for Transport, Energy and Infrastructure (South Australia). Discussions with these road authorities concluded that each authority undertakes its own risk assessment for each site and the requirement for a road safety barrier is determined from this investigation. Further, these risk assessments often result in varying levels of protection by barriers at similar sites. Of note, in Western Australia, the Southern Suburbs Railway from Perth to Mandurah has a railway in the central median of the freeway. The road safety barriers used are a combination of Test Level 3 3 wire rope and Test Level 5 concrete barriers. Where a wire rope barrier can be accommodated (i.e. where there is a 3 metre deflection area available from the barrier to the rail clearance envelope) it has been used. Otherwise, a Test Level 5 concrete barrier has been adopted. The test levels were determined using a benefit cost model developed for the project by risk consultants. The model considered: � The likely number of penetrations of the various barrier test levels, � The costs associated with the various barrier performance levels (due to the small

cost difference between a Test Level 4 and Test Level 5 concrete barrier, the Test Level 5 barrier was determined as the most suitable concrete barrier test level), and

� Reducing the risk level to as low as practicable to both road users and passengers/operators of the train.

INTERNATIONAL LITERATURE REVIEW There was little international literature published on this subject. Generally, the roadside design procedures used around the world are limited to describing where a barrier is required to protect the occupants of the impacting vehicle. However, where a road passes a school or infrastructure that requires protection, an engineer may specify a higher containment barrier or may recommend the installation of a barrier even if the school or other infrastructure is outside the recommended clear zone. For bridge barriers, the usual procedures relate to the mass and type of vehicle to be restrained and the height of the bridge and what it spans. A presentation by A V Martinez (HIASA, Spain), stated that the German guidelines4 for road users to be protected adequately had requirements for the limiting distance, between the edge of the carriageway and the hazard. A second condition was tested when there a third party hazard is present nearby. Third party hazards are divided into two categories depending on the risk. The higher risk category includes

3 Refer to Australian Standard AS 3845 (1999) for information about test levels.

4 Refer to Richtlinen fur passiven Schutz an StraBen durch Fahrzeug-Ruckhaltesysteme, RPS 2003


chemical plants with high explosives, very crowded areas and parallel railway with high-speed trains. The lower risk category includes pedestrian and cycle-ways with heavy usage, parallel railways with more than 30 trains (but not high speed trains) in 24 hours and parallel roadways with more than 500 vehicles per day. If there were fewer than 30 lower-speed trains in 24 hours then it would not be considered a significant third party hazard. The German guidelines require a barrier to be used in the conditions described in Figure 1.

5

7.5

12

8

12

20

0

5

10

15

20

25

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

Vehicle speed

Dis

tan

ce b

etw

een

th

e c

arr

iag

ew

ay a

nd

the h

azard

(m

)

Vehicle occupant protection Third party hazard

Figure 1. Summary of German guidelines for the minimum distance between the hazard and the road for a barrier not to be required.

As well as specifying that a barrier is required, the German guidelines indicate the type of barrier to be used. These requirements are listed in Table 2. Risk category

Condition Truck volume CEN 1317 Test level

Equivalent NCHRP 350 Test level

High Speeds > 50 km/h – High accident risk or a ‘blackspot’

> 3000 trucks / day H4b TL6

< 3000 trucks / day H2 TL4

Speeds > 50 km/h – Not a high accident risk or ‘blackspot’

> 3000 trucks / day H2 TL4 < 3000 trucks / day H1 TL2 – TL3

Speeds < 50 km/h No barrier required

Low Speeds between 60 and 70 km/h – High accident risk or a ‘blackspot’ and > 3000 veh/day

> 500 trucks / day H1 TL2 – TL3

< 500 trucks / day N2 TL2

Speeds between 80 and 100 km/h – >3000 veh/day

> 500 trucks / day H1 TL2 – TL3 < 500 trucks / day N2 TL2

Speeds > 100 km/h > 3000 trucks / day H2 TL2

< 3000 trucks / day H1 TL2 – TL3

Table 2. German guidelines for protecting third party ‘hazard’

It is for noting that the German guidelines for barrier strength are similar to those specified in the Spanish guidelines.


The RISER (Roadside Infrastructure for Safer European Roads)5 project report states that: “III.4.2 Railway tracks In Great Britain, a railway track at the foot of an embankment should also be protected, according to IRRRS. In Sweden, the safety zone should be modified when the road passes near a railway track. In general the edge of a motorway should be more than 25m to the centreline of a railway track.” The other major reference is the UK process known as RRRAP (Road Restraint Risk Assessment Process). This process is implemented using a spreadsheet and considers a number of inputs and advises on the appropriate barrier for conditions. The hazard is described by a series of lines with the intersecting points between the lines being defined as an offset to the road. The specification of the hazard type and characteristics is extensive. The RRRAP process recognises that the railways may need additional consideration. The Guide 6 states “when other parties are involved, as in the case of railways, there will often be a reduction of risk level by providing a higher containment, though the benefit cost of so doing may be low. If the initial risk level is low, there will be little reduction in risk from using higher containments, and in some instances the level of risk will increase with the higher containment safety barrier, as it is a hazard in itself.” Consequently, the containment level of the barrier may change but the issue of whether or not to use a barrier is not affected. The authors used the RRRAP to assess the minimum distance required between the road and the railway system that it gave for particular scenarios. The assessment considered that the road was a major rural motorway with a speed limit of 70 mph (113 km/h) and a one-way volume of 20,000 vehicles per day. The railway was running parallel to the road. RRRAP requires a number of different descriptors of the road and railway characteristics. For instance, the road alignment, being a motorway, was considered to have a good alignment defined as having “full standard sight stopping distance (SSD), full width lanes, straight and constant grade”. The site was affected by drivers’ fatigue as the site was at the end of a long route. The mean speed was considered approximately equal to the speed limit. The railway was at a similar level to the roadway and there were no intervening roadside features that would cause an errant vehicle to be diverted or to be slowed before reaching the railway. It was also investigated whether this last parameter had a significant effect on the outcome. The railway had multiple tracks and with line speeds of up to 125 mph or 201 km/h (or curved tracks to 100 mph or 161 km/h). The output from RRRAP for the appropriate barrier for different lateral distances between the corridors is listed in Table 3. Note, barrier containment level N2 is a

5 RISER Consortium 2003, “Report D05: Summary of European design guidelines for roadside infrastructure”. European Road

Federation, Brussels, Belgium 6 Highways Agency, Scottish Executive Development Department, National Assembly for Wales & Department for Regional

Development Northern Ireland 2007, “Road Restraint Risk Assessment Process (RRRAP) Process and Guide”, Highways Agency, London.


European standard (EN1317) which is roughly equivalent to TL 3 and W2 refers to a working width of 0.8 m. The result from RRRAP indicated that, for a high-speed motorway adjacent to a high-speed rail corridor, a distance of more than 18 to 20 m separation did not require a barrier. Further, the appropriate separation between corridors and the barrier type will be influenced by the types of vehicles using the roads.

Offset of hazard (m)

Is risk without Vehicle

Restraint System

acceptable?

Barrier Containment

level

Barrier working

width class

Barrier working width (m)

Offset of Barrier from

the edge of the carriageway

Reasonable chance of getting to the rail line 5.00 No N2 W2 0.80 1.20

10.00 No N2 W2 0.80 1.20

12.00 No N2 W2 0.80 1.20

13.00 No N2 W2 0.80 1.20

14.00 Yes Almost certain of getting to the rail line

17.00 No N2 W2 0.80 1.20 18.00 Yes

Table 3. Results from RRRAP

AUSTRALIAN STANDARDS AND GUIDELINES REVIEW The Australian Standard for Road Safety Barrier Systems, AS 3845, and the Australian Standard for Bridge Design, AS 5100 and Austroads “Guide to Road Design: Safety Barriers” were reviewed to obtain guidance on acceptable road and bridge barriers at the rail and road interface. AS 3845 gives guidance on what constitutes an acceptable barrier in terms of longitudinal barrier type, barrier end treatments, vehicle containment and test requirements, material properties, and maintenance. It also provides some guidance on when a barrier should be used or where it should be located. Austroads is preparing a guide on this topic that is still in draft. They all use a risk profile based on the following assumptions: � A single road vehicle with 1 or 2 occupants, � A clear zone at the side of the road to enable vehicle recovery, � The focus is on the risk to the occupant(s) of the vehicle only, and � The vehicle is not intentionally driven off the road (e.g. act of terrorism) These three documents define the need for a barrier, mainly concerning the road type, design and traffic volume but generally not about what is on the other side of the barrier. Some of the exclusions include: � High occupancy vehicles, e.g. buses and trains, � Other assets of significance, e.g. buildings, school grounds, electrical substations,

and railway control centres that may be impacted by an errant vehicle, � Adjacent transport corridors such as parallel roads and railways, or � Grade separated corridors, e.g. a road overpass over another road or a rail

corridor where a vehicle may leave one corridor and impact the other corridor. AS 5100 bases its design criteria on the following:


� A single road vehicle involved only, � The road alignment (including the carriageway width, and whether it is straight or

curved), � The depth of water where appropriate, � The height of the bridge above the ground, � The traffic volume, � The type of vehicles, and � The design speed of the road. AS 5100 does not consider: � High occupancy vehicles (e.g. high speed passenger trains), � The presence of high risk buildings next to an elevated structure (e.g. a control

room for train network), � Special vehicles (e.g. double-decker road train), � The transition from a road to a bridge barrier in detail (there is only a high level

overview). SUMMARY OF NATIONAL AND INTERNATIONAL PRACTICE REVIEW The main conclusion from the national and international practice review is that, a risk assessment is undertaken for each site and that the decision regarding whether a barrier is required be made using a first principles risk assessment. It was noted that there are three factors that combine to give the level of risk at a particular location – the frequency of vehicles leaving the road, the probability of a vehicle reaching the railway line and the consequences in terms of death and injury as a result. From the Standards and Guidelines review, Australian Standards AS 3845 and AS 5100 and the Draft Austroads “Guide to Road Design: Safety Barriers”, currently only provide guidance on the treatment of roadside hazards predominantly to the road user, including the use of road safety barriers and advice on appropriate roadside furniture. These documents have limitations and this paper extends the scope of the use of road safety barriers. METHODOLOGY FOR GUIDELINE The QMR and QR Network working group was set up to develop a guideline that could be adopted by designers to determine the appropriate road and bridge barrier where the road and the rail are in close proximity without having to go back to first principles each time. The objective for the research was to codify the minimum requirements for road and bridge barrier where the road and rail corridors are in close proximity. The solution had to be acceptable to both the road and rail authorities. The methodology includes a road/rail barrier selection matrix developed using a risk assessment methodology. It has been further supplemented with a systematic procedure for barrier selection in parallel road and rail corridors and a document on road barrier selection for bridges over rail corridors. A road safety barrier is installed, as a last resort, to shield a hazard with the requirement that the occupants be less likely to be injured with a collision with the safety barrier instead of a collision with a hazard. Other engineering techniques that reduce the potential severity of a collision of the hazard should be considered first.


Adequate road design geometry and considerations on delineation, pavement markings and warning signs, based on the 85th percentile speed and not the posted speed, may reduce the likelihood of a vehicle leaving the road and reaching a rail corridor. Driver fatigue zones affect the likelihood of a vehicle leaving the road and reaching a rail corridor. Consequently, the process accounts for driver fatigue with an increased level of protection. A bridge barrier is selected on the consequences of a vehicle not being redirected by the barrier. Bridge barrier designs results in stiffer, less forgiving structures compared with roadside barriers shielding, for instance, a tree; all other factors being equal. In this, the designer balances an increased risk to occupants of impacting road vehicles and decreases the risk of the vehicle finishing its errant path in the water. The process described here extends this notion to roadside barriers based on the consequences of a vehicle entering the railway reserve. Assumptions for the work presented in the paper are: � The errant vehicle is assumed to have 1 or 2 occupant(s), and � Trucks are assumed to be a 36 tonne tanker semi-trailer. Exclusions from this work include: � Level Crossings, � “High centre of gravity” vehicles such as double-decker cattle trucks. Where

these vehicles form part of the traffic streams (e.g. western Queensland, Northern Territory and north-western Western Australia) then the height of barriers need to be re-evaluated, and

� Length of barrier required on bridge approaches. Although the procedure could be used for sites with special structures in the rail corridor including signal boxes, these sites may require additional analysis and assessment if the damage to these facilities could disable a significant part of the rail network. Similarly, areas with a higher expected frequency of drivers leaving the road may also need additional analysis; off-ramps with tight curves for example. BASIC METHODOLOGY FOR ROADSIDE BARRIERS The type of barrier required is a function of the effective distance between the edge of the outer road lane and the rail infrastructure (for instance rail track and its status or usage of the road and rail corridor). The effective distance is equal to the measured distance, if there are no horizontal curves or embankment slopes between the road and railway. The measured distance between the edge of the outer road lane and the rail infrastructure is adjusted by factors to account for horizontal road curves and embankment slopes. After applying these factors, the measure becomes the effective separation between the corridors. The approach described here differs from the assessment of barriers on the roadside away from rail corridors. In this case, hazards would be protected if they were in the clear zone and the width of the clear zone is modified by various factors. For instance, where the road had a horizontal curve, then the clear zone would be increased.


SPEED ENVIRONMENT The barrier selection matrix has been formulated for use on roads with a constant speed environment, where the roads are aligned parallel to a rail corridor. Situations where there is a transition from a high speed environment to a low speed environment, such as off-ramps, would need additional consideration including factors such as curve radius, available side friction on the road, cross-fall, etc. ROAD AND RAIL STATUS The road and rail corridors were generally classified by their use, location and broad geometry. This established a hierarchy for railways and roads listed in Tables 4 and 5. Accordingly, these criteria were used in the barrier selection matrixes as follows.

Railway status

Description

MPE Main-line electrified (high passenger train frequency), i.e. the suburban network

MC & DG Main country passenger and goods lines (eg. NCL) & light trafficked dangerous goods lines (i.e. explosive or highly flammable)

SP Secondary passenger and/or goods lines. 1-5 trains / 24 hours

L Light country lines < 7 trains per week

C Coal/mineral lines

Table 4. Railway Status

Road status

Description Speed (km/h)

Traffic volume (veh/day)

1A Arterial & dual carriageway 110 100,000

1B Arterial & dual carriageway 80 70,000

1C Arterial & dual carriageway 60 50,000

2A Arterial, connection roads and rural highways 110 50,000

2B Arterial, connection roads and rural highways 80 30,000

2C Urban road 70 10,000

3 Residential Street 60 1,000

Table 5. Road/Road Bridge Overpass Status

BRIDGE BARRIER DESIGN The choice of barriers is aligned to AS 5100. Barriers are to be located within the road corridor adjacent to the road shoulder. The designer must consider the following: � The barrier strength necessary to stop the vehicle or its load penetrating the

barrier. � Barrier height to minimise the risk of the vehicle or its load being propelled over it. � Containment of debris from any secondary vehicle collisions within the road

corridor. � Limiting the impact of any fire within the road corridor from adversely impacting on

railway operations. A 36 tonne articulated tanker was nominated as the controlling vehicle, as it is one of the largest vehicles commonly found on the road network. The performance level,


loads and contact heights all conform to AS 5100. (Refer to Table 6). Barrier heights in excess of 1.1m were determined to stop vehicles rolling over the barrier. The effective height of the transverse load, 50mm below the height of the barrier, conforms to AS 3845. This value has been adopted for bridge barriers to provide consistency between the standards.

Barrier Performance

Level

Barrier height

(m)

Effective height He

of transverse load (m)**

Transverse Load (kN)

Vehicle Contact Length (m)***

Regular 1.1 1.05 250 1.1 (AS 5100.2 Table 11.2.2)

Medium 1.1 1.05 500 2.4 (AS 5100.2 Table A1)

Medium 1.5 1.45 500 2.4 (AS 5100.2 Table A1)

Special 1.5 1.45 750 2.4 (AS 5100.2 Table A2)

Special* 1.5 1.45 1000 2.5 (AS 5100.2 Table A2)

Special* 2.0 1.95 1000 2.5 (AS 5100.2 Table A2)

Notes to table: * 44 t articulated truck ** Length of barrier that vehicle load is applied over. *** Refer to AS3845 Figure 3.5 "Dimensions"

Table 6. Application of loads to road bridge safety barriers

Table 4 groups the trains in terms of speed, frequency, and risk. A high-speed commuter line has a greater risk than an infrequently used low speed rural branch line. Similarly, Table 5 has classified road traffic in terms of speed, traffic volume and importance level. Table 7 is the matrix that determines the barrier height and performance level based on the road and rail line classification derived from AS 5100.

Road Status Barrier Height (m) and Barrier Performance Level to AS 5100

1A 2.0 (Special) 1.5 (Special) 1.5 (Medium) 1.1 (Medium) 1.5 (Special)

1B 1.5 (Special) 1.5 (Medium) 1.1 (Medium) 1.1 (Regular) 1.5 (Medium)

1C 1.5 (Special) 1.5 (Medium) 1.1 (Medium) 1.1 (Regular) 1.5 (Medium)

2A 1.5 (Special) 1.5 (Medium) 1.5 (Medium) 1.1 (Medium) 1.5 (Medium)

2B 1.5 (Special) 1.5 (Medium) 1.1 (Medium) 1.1 (Regular) 1.1 (Medium)

2C 1.5 (Medium) 1.1 (Medium) 1.1 (Regular) 1.1 (Regular) 1.1 (Medium)

3 1.1 (Regular) 1.1 (Regular) 1.1 (Regular) 1.1 (Regular) 1.1 (Regular)

Rail Status MPE MC & DG SP L C

Note: [1.1 (Regular)] denotes the barrier is 1100mm high, measured from the edge of the adjacent road lane pavement level with a barrier performance level "Regular".

Table 7. Barrier Height and Barrier Performance Level Selection for Road Bridge Over Rail

BRIDGES OVER RAILWAY CORRIDOR Suitable reinforced concrete barriers are to be provided over the full length of the railway corridor on both sides of road over rail bridges and on bridge approaches (the length of the approach barrier is to be determined by a risk assessment). The Rail Authority may allow the barrier to span the railway corridor partially, based on the current and future frequency of rail traffic and other railway activity in the railway corridor. (Refer to Figure 2.) The bridge barrier selection is based on Table 7 as discussed previously. Transition barriers are to be provided on both ends of the bridge barrier, refer to Figure 2, and AS 5100 for further information.


Figure 2. Road bridge over railway corridor

The possible future rail and road status needs to be taken into consideration in the barrier selection process and accordingly the bridge designed to accommodate future barrier requirements as well. ROAD BARRIER DESIGN A number of different performance level barriers were selected as being suitable for third party protection. These are listed in Table 8 and range from the Test level 4 (TL4) barriers specified in the AS 3845 to barriers typically used as bridge barriers and denoted as test level 6 (TL6) barriers. TL4 and TL5 barriers can be selected from established proprietary and non-proprietary safety barrier designs. The 1.5 m high TL5 and TL6 barriers must be designed in accordance with the Bridge Design Standard AS 5100.

Barrier Performance Level

Height (m)

Effective height He (m) **

Transverse Load (kN)

Vehicle Contact Length (m)***

TL4 0.8

"Road Safety Barriers and End Treatments, assessed as compliant with AS/NZS3845:1999"

TL4 1.1

TL5 1.1

TL5 1.5 1.40 500 2.4 (AS5100.2 Table A2)

TL6 1.5 1.40 750 2.4 (AS5100.2 Table A2)

TL6* 1.5 1.40 1000 2.5 (AS5100.2 Table A2)

TL6** 2.0**** 1.40 1000 2.5 (AS5100.2 Table A2)

Notes: * Based on impacts by a 44 t articulated vehicle ** The effective height indicates the height that the load is applied *** The contact length is the length over which the load is distributed **** This barrier is higher to protect against fires and load movement during an impact, however the

strength of the barrier required to redirect the vehicle remains 1.4 m from the datum.

Table 8. Application of loads to road safety barriers

The road/rail interface barrier selection matrix, Table 10, shows the different road and rail corridor characteristics ordered into groups with approximately the same risk. The bridge barrier selection matrix, Table 7, was used as a starting point. The relative risk level matrix in Table 9 was used to develop road/rail interface barrier selection matrix. As the usage on the road or the rail corridor decreased and as the


speed of vehicles on the road decreased so did the risk level (as shown by a lower number in Table 9).

Road Status

Relative Risk Level for different road and rail corridors

1A RL10 RL8 RL6 RL5 RL8

1B RL9 RL7 RL5 RL4 RL6

1C RL8 RL6 RL5 RL6 RL6

2A RL9 RL7 RL6 RL5 RL6

2B RL8 RL6 RL5 RL3 RL5

2C RL6 RL5 RL4 RL3 RL4

3 RL4 RL3 RL2 RL1 RL2

Rail Status

MPE MC & DG SP L C

Note: Higher number is a higher risk

Table 9. Relative Risk level for different road and rail status corridors.

Risk level 1 (RL1), the lowest level, had protection that would be similar to a rural road with substantial truck traffic. The protection for risk level 10 was established after substantial discussion between the organisations. The effective horizontal distance is the measured horizontal distance from the edge of the nearest road lane to the rail infrastructure; modified by curve or slope factors where necessary. (This is discussed in more detail below.) The minimum effective horizontal offset between the road and rail corridors where a barrier is not required is similar although slightly greater than the offset used in other countries. The roadside barrier specified for a rail and road corridor closer than 5 m should be the same as for a bridge barrier. The exception was for the Main Line Electrified rail corridor with high passenger train frequency and a high-speed road. In this case, the barrier is higher at the roadside as there is a greater risk of a vehicle fire affecting the operation of the rail network. It is considered that these dimensions are practical and provide a high level of safety for both road users and rail operators and travellers.


Ro

ad

/R

ail

co

rrid

or

ch

ara

cte

ris

tic

s

1A-MPE 1B-MPE 1C-MPE 1B-MC 1C-MC 2C-MC 2C-SP 1C-L 3-SP 3-L

2A-MPE 1A-MC 2A-MC 2B-MC 1B-SP 2C-C 2B-L 3-C

1A-C 1A-SP 2B-SP 1B-L 2C-L

2B-MPE 2A-SP 2B-C 3-MPE 3-MC

2A-C 1A-L

1B-C 2A-L

2C-MPE 1C-SP

1C-C

Relative Risk level

RL10 RL9 RL8 RL7 RL6 RL5 RL4 RL3 RL2 RL1

Eff

ec

tiv

e H

ori

zo

nta

l d

ista

nc

e,

XE

(m

)

4 TL6 2.0 TL6 1.5 TL6 1.5 TL5 1.5 TL5 1.5 TL5 1.1 TL4 1.1 TL4 1.1 TL4 1.1

5 TL6 2.0 TL6 1.5 TL6 1.5 TL5 1.5 TL5 1.5 TL5 1.1 TL4 1.1 TL4 1.1 TL4 0.8

6 TL6 2.0 TL6 1.5 TL6 1.5 TL5 1.5 TL5 1.5 TL5 1.1 TL4 1.1 TL4 0.8

7 TL6 1.5 TL6 1.5 TL5 1.5 TL5 1.5 TL5 1.5 TL4 1.1 TL4 0.8

8 TL6 1.5 TL5 1.5 TL5 1.5 TL5 1.5 TL5 1.1 TL4 1.1

9 TL5 1.5 TL5 1.5 TL5 1.5 TL5 1.1 TL5 1.1 TL4 0.8

10 TL5 1.5 TL5 1.5 TL5 1.5 TL5 1.1 TL5 1.1

11 TL5 1.5 TL5 1.5 TL5 1.1 TL5 1.1 TL4 1.1

12 TL5 1.5 TL5 1.1 TL5 1.1 TL5 1.1 TL4 1.1

13 TL5 1.1 TL5 1.1 TL5 1.1 TL5 1.1 TL4 1.1

14 TL5 1.1 TL5 1.1 TL5 1.1 TL4 1.1 TL4 0.8

15 TL5 1.1 TL5 1.1 TL4 1.1 TL4 1.1

16 TL5 1.1 TL5 1.1 TL4 1.1 TL4 1.1

17 TL5 1.1 TL5 1.1 TL4 1.1 TL4 0.8

18 TL5 1.1 TL4 1.1 TL4 1.1 TL4 0.8

19 TL4 1.1 TL4 1.1 TL4 0.8

20 TL4 1.1 TL4 1.1 TL4 0.8

21 TL4 1.1 TL4 1.1

22 TL4 1.1 TL4 1.1

23 TL4 1.1 TL4 0.8

24 TL4 1.1 TL4 0.8

25 TL4 0.8

26 TL4 0.8

27 TL4 0.8

28

29

30

31 Note: Light Green shaded area denotes that a barrier may be required where directed by the Road and/or Rail authority as

determined by a risk assessment.

32

33

34

35

Note: The distance from the road to the rail corridor is measured from the edge of the road carriageway to the nearest track centreline or to nearest part of structure of high importance

Table 10. Road/Rail interface barrier selection


HORIZONTAL CURVE CONVERSION FACTORS Using the concepts in AASHTO Roadside Design Guide7, the number of vehicles encroaching onto the verge will increase as the curvature of the horizontal curve increases. The adjustment factors are used to increase the clear zone at horizontal curves and are equal to 1.0 at nil curvature (a straight road). A conversion factor between the measured distance and the effective distance was developed from the typical clear zone adjustment values used by Australian road authorities. These conversion values are shown in Table 11. The measured horizontal distance is divided by the curve correction factor to obtain the effective offset. If a horizontal curve has a tight radius, then the conversion factor will be small and the effective distance will be decreased. This will result in a higher level of protection being warranted. As an example, if the measured distance between the corridors was 25 m, the horizontal curve radius on the road was 600 m and the operating speed was 100 km/h, then the effective distance between the corridors would be 25 x 0.78 or 19.5 m.

Radii (m) 60 km/h 70 km/h 80 km/h 90 km/h 100 km/h 110 km/h

100 0.56 0.50 0.43 * * *

150 0.66 0.60 0.54 0.47 0.41 *

200 0.72 0.67 0.61 0.54 0.48 0.41

250 0.76 0.71 0.66 0.60 0.53 0.47

300 0.80 0.75 0.70 0.64 0.58 0.51

400 0.84 0.80 0.75 0.70 0.65 0.58

500 0.87 0.83 0.79 0.75 0.69 0.64

600 0.89 0.86 0.82 0.78 0.73 0.68

700 0.90 0.88 0.84 0.81 0.76 0.71

800 0.91 0.89 0.86 0.83 0.78 0.74

Note: * Not permitted

Table 11. Horizontal Curve Correction Factors

SLOPE ADJUSTMENT

Drivers can lose control of a vehicle travelling down an embankment and this may increase the chance of a vehicle reaching a railway track. Conversely, an uphill embankment will reduce the possibility of a vehicle reaching the rail line. The approach for adjusting the measured distance between the corridors to account for different embankments slopes allows a full consideration of the site’s topography as it includes: � gradient of side slope, � distance from toe of embankment to the nearest railway line, and � elevation of track in comparison to approach slopes. Overall, Table 10 lists the recommended roadside barrier to be used for different road and rail usage and for different effective distances between the road and rail

7 American Association of State Highway and Transportation Officials (AASHTO) 1989 “Roadside Design Guide” AASHTO,

Washington, D.C.


corridors. The effective horizontal distance between the corridors is a function of the measured distance and adjustment factors and coefficients. PROTECTION OF SPECIAL STRUCTURES IN RAIL CORRIDORS Some individual structures in rail corridors (for example, signal boxes, transformers) may require local protection (for example, earth mounds, safety barriers or strengthening of the structure itself). The solution will need to be determined by a risk analysis on a case-by-case basis. APPLICATION Both authorities have worked together on a series of projects including: � the Port of Brisbane Motorway adjacent to the rail line to the Port of Brisbane, � four alliances on the Western Transport Corridor in Brisbane where the Ipswich

passenger line is adjacent and/or crosses the Ipswich Motorway, � the combined Springfield Corridor, and � the Multi Modal Transport Corridor at the Sunshine Coast These projects have provided an extensive range of situations. Close co-operation has resulted in the development and refinement of the design criteria presented in this paper and allowed for post-evaluation of the completed project. A number of other locations have also been used for audit testing of the guideline to confirm the validity of the assumptions, limitations and exclusions. FUTURE EXTENSION OF WORK There are a number of scenarios that are to be developed as a future extension to the guideline: � The work for road/rail bridge barriers can easily be extended to road over road

(i.e. road over expressway) situations, � Off-ramps, � Higher “centre of gravity” vehicles and B-triples, and � Length of barrier on bridge approaches. EXCLUSIONS FROM THIS WORK The following conditions have not been considered: � Railway level crossings, and � Barriers adjacent to construction zones. CONCLUSIONS This paper has clearly defined the risk profile for barriers in: � road corridors, � rail corridors, and � combined road and rail corridors The current Australian Standards for road and bridge barriers, AS 3845 and AS 5100, have been written from the perspective of a road authority. Both standards, as currently written, do not adequately define their applicability. This paper has clarified the applicability of the standards. Additionally, this paper has extended the design criteria to encompass combined road and rail corridors. The work has adopted current standard barrier designs and applied them to multi modal transport corridors. It is recommended that the outcomes of this paper be adopted by Standards


Australia and Austroads and be incorporated in future revisions of the standards and guidelines. This work has extended the knowledge of barrier design, identified areas for future extension of this work and defined exclusion for the implementation of current barrier designs. The recommended changes have been trialled on actual major projects. This has streamlined the design process and resulted in a better standard of protection for road and rail users.

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