Recommendations on Multi Storey Car Park Design

8/7/2019 Recommendations on Multi Storey Car Park Design

1/59

The Institution of Structural Engineers andThe Institution ofHighways and TransportationJANUARY 1984

Designrecommendations formulti-storey andunderground car parks(2nd edition)

Published by the Institution of Structural Engineers


2/59

11 UPPER BELGRAVE STREET, LONDON SW1X 8BH

The Institution of Structural Engineers andThe Institution ofHighways and Transportation

Designrecommendations formulti-storey andunderground car parks(2nd edition)

JANUARY 1984

The Institution of Structural Engineers


3/59

Constitution ofJoint Committee

D. R. Sharp, OBE, DSc, DipTP(Lond), CEng, FIStructE, FICE, FIMunE, FIHT (Chairman)John Campbell, MCIBSK. J. C. Clayden, BSc, CEng, FlStructE, FICE, FIHTE. W. Dore, CEng, FlStructE, MICE, MIMunEA. F. Gee, MA, CEng, FIStructE, FICE, FlMechE, FIHTJohn Glanville, BSc(Eng), ACGI, CEng, FICE, FIHTW. E. A. Skinner, CEng, FIStructE, FICE, FHKIEW. P. Winston, BSc(Tech), CEng, FlCE, FIHT, M ASCER. J. W. Milne, BSc (Secretary)

2nd edition published January 1984; reprinted December 1988 with new style cover and title page 1984:The Institution of Structural EngineersThis publication iscopyright under the Berne Convention and the InternationalCopyright Convention. All rights reserved. Apart from any copying under the UKCopyright Act 1956, part 1,section 7, whereby a single copy of an article may besupplied, under certain conditions, for the purposes of research or private study, byalibrary of a class prescribed by the UK Board of Trade Regulations (StatutoryInstruments, 1957, no. 868), no part of this publication may be reproduced, stored ina retrieval system or transmitted in any form or by any means without priorpermission of the copyright owners. Permission isnot, however, required to copyextracts on conditions that a full reference to the source isshown.Multiple copying of the contents of the publication without permission contravenes theaforementioned Act.


4/59

Contents

FOREWORD 5 Parking angle 1 6Layout controls 1 6GLOSSARY 6 Parking-area layout 1 6Ramps 1 81 CLIENT'S BRIEF AND PERFORMANCE Entrances and exits 1 8SPECIFICATION 7 Choice of layout 1 91 . 1 Introduction 7 3 . 5 Dynamic requirements 1 9Scope 7 Procedure 1 9Mixed-use structures 7 Traffic demand 1 9Limitations imposed by statutory Dynamic capacity 1 9requirements and public policy 7 Vehicle speed 1 9Design brief 7 Capacities of aisles and stalls 1 91 . 2 Information to be considered for inclusion Time taken to park, and stall width 2 0in the brief 7 Parking angle 2 0

The aim 7 Ramp capacity 2 0The site 7 Accessway and carriageway capacity 2 0Site conditions 7 Bends on access way and ramps 2 0Highway access 7 Entrance-barrier capacity 2 0Statutory undertakers 7 Vehicle reservoir at entrance, andRe-use 8 entrance layout 2 1Submission of the design and costs 8 Exit-barrier capacity 2 11 . 3 Design considerations 8 Exit capacity 2 1Structural 8 Vehicle reservoir at exit 2 1Environmental 8 Turnover 2 3Town planning 8Building regulations 8 4 VEHICULAR AND PEDESTRIAN1 . 4 Performance specification 8 CONTROL 2 5General 8 4 . 1 Vehicle control 2 5Traffic feasibility requirements 8 Introduction 2 5Site feasibility requirements 8 Entry control 2 5Accommodation and operational requirements 8 Capacity of entry lanes 2 5Schedule 8 Control within the car park 2 5Choice of solution 9 Signs 2 6Vehicle safety barriers 2 6

2 APPEARANCE AND PLANNING 10 Collection of parking fees 2 6Fraud 2 63 DESIGN GEOMETRY Methods of payment 2 61 2 Control of exit 2 7

3 . 1 Introduction 1 2 Exit capacities 2 73 . 2 The car 1 2 4 . 2 Pedestrian control 2 73 . 3 Static requirements 13 Introduction 2 7Stall width, stall length, aisle width Pedestrian/vehicle conflict 2 8and bin width 13 Stair and lift shafts 2 8Side clearances on structure 13 Ramps 2 8Columns 13 Aisles 2 8Height 1 4 Lifts 2 8Floor gradient 1 4 Disabled persons 2 9Ramp and access way gradients 1 4Ramp and accessway curvature, widths 5 DESIGN AND CONSTRUCTION OFand clearance on structure 1 4 CARPARKS 3 0Superelevation 1 4 5 . 1 Classification of above-ground car parks 3 0Kerb height 1 4 5 . 2 Materials and methods of constructionEntry and exit arrangements 1 4 for above-ground car parks 3 03 . 4 Layout of car parks 1 5 Materials 3 0Principles 1 5 Concrete construction 3 0Cul-de-sac parking 1 6 Steel construction 3 0One- and two-way aisles 1 6 Composite construction 3 0


5/59

5.3 Constraints in above-ground car parks 30 7 FIRE CONSIDERATIONS 44Column positions 30 7.1 Fire prevention 44Loading 30 7.2 Fire resistance 445.4 Design solutions for above-ground carparks 30 7.3 Fire detection and extinguishing equipment 44Precast concrete 30 General 44In situ concrete 31 Sprinklers 45Composite construction 31 Automatic fire alarms 455.5 Structural discontinuities in above-ground Hand appliances 45carparks 34 7.4 Means of escape 45Movement joints (full lateral discontinuity) 34 Governing bodies 45Foundations 35 Rules for guidance 45Deflection limits 35Stability 355.6 Cladding 35General 35 8 WATERPROOFING, DRAINAGE,Categories of cladding 35 FLOOR FINISHES ANDFixings 36 MAINTENANCE 475.7 Underground car parks 36 8.1 Waterproofing 475.8 Design criteria for underground car parks 36 General 47Geometry and circulation 36 Alternative approaches to waterproofing 47Fireprecautions 36 Concrete deck slabs without waterproofSmoke precautions and extraction 37 membrane 47Mechanical services 37 Concrete deck waterproofed by use of aNoise 37 membrane 48Drainage 38 Vulnerable details 51Site investigation 38 Movement joints 515.9 Methods of construction and structural 8.2 Drainage 52design for underground car parks 38 Introduction 52General 38 The roof 52Types of carpark 38 Intermediate floors 52Methods of construction 38 8.3 Floor finishes 525.10 Landscaping of underground car parks 38 Introduction 52Design criteria 38 Underground floors 52Control of moisture conditions 38 Line and level 52After-care 39 Typical floor specifications 53Waterfeatures 39 Curing concrete floors 54Cold-weather construction 54

6 LIGHTING, HEATING AND Hot- weather construction 54VENTILATION 40 Admixtures

546.1 Lighting 40 Precautions against snow and ice 54General 40 Floor hardeners 54Illumination standards 40 Special surfaces 54Selection of electrical equipment 8.4 Maintenance ofwaterproofing and floors 55(general requirements) 40 Definition of maintenance 55Choice of luminaires 41 Designer's interest inmaintenance 55Circuit arrangement 41 Cost of ignoring the need for maintenance 556.2 Heating 41 Premature failures 55General 41 Maintenance staff 55Ramps 41 8.5 Conclusion 55Roofs 42Space heating 426.3 Ventilation 42

Reasons for ventilation 42 9 CAR PARKS OUTSIDE THENatural ventilation 42 UNITED KINGDOM 56Mechanical ventilation 42Noise levels 43General recommendations 43 REFERENCES 57


6/59

Foreword

In May 1973the Institution of Structural Engineers and the Institution ofHighwayEngineers, as it was then, held a conference in London on the subject ofmulti-storey and underground car parks, where the emphasis was on design. Theinformation presented at this conference was clearly of considerable value, andthe two Institutions therefore appointed a Joint Committee to prepare compre-hensive recommendations on design, using the conference proceedings as astarting point. The Committee moved very quickly, and in December 1975 theJoint Report was published by the Institution of Structural Engineers on behalf ofthe two Institutions.It was clear from the beginning that the document filled a considerable gap, andit is probably true to say that it became the standard work on the subject in the UKand in many countries overseas, particularly where British designers haveinfluence. The best recommendations date with time, and it was thereforeinevitable that the two Institutions should decide that a revision should beundertaken. The result is this report.The original Committee comprised eight members with the invaluable supportof the Assistant Secretary (Technical) of the Institution of Structural Engineers.We were extremely fortunate for the revision in that all the original members ofthe Joint Committee were available, with one exception, thus ensuring thegreatest amount of continuity. Although the original report has stood up well to

the passage of time, the opportunity has been taken in the new edition, not only toupdate the information originally presented, but also to introduce new data andideas. The Joint Committee welcomes feedback from users of the report.

December 1983 D. R. SHARP, Chairman, lointCommittee

5


7/59

Glossary

A ccessway

Aisle

Bin

Clearway ramp

Dynamic capacity

Parking angle

Ramp

Reservoir

Stall

Static capacity

6

Carriageway not adjoining stalls and used solely for the movement of vehicles.

An accessway serving adjoining stalls.

Two rows of stalls with the access aisle running between them. A half-bin is one row of stallsand the aisle serving them.

A ramp system that does not include an aisle in its circulation and which providesunencumbered access between the parking floors and an entrance or exit.

This term may be applied either to the individual parts of a car park or to a car park as a whole.It is the maximum flow of cars, or where appropriate people, which the part of the car park orthe car park as a whole as the case may be, can accommodate.

The angle between the length of a stall and the aisle from which it is served.

An accessway or aisle connecting parking areas at different levels. More usually the term isapplied to accessways only.

An accessway where cars may queue without obstructing movements in other parts of a carpark or the external road system. A reservoir may also be described as a vehicle reservoir.

The parking area, exclusive of aisle or other adjoining area, allocated to one car.

The total number of stalls in a car park.


8/59

Client's brief andperformance specification1

11 IntroductionScopeThese notes are designed to assist the client who wishesto commission a design for a car-parking facility eitherabove or below ground and operated on the direct-flowramp principle. Single-level parking lots are not specifi-cally dealt with; mechanically-operated stacking deviceshave been excluded. Nevertheless much of the informa-tion required for these two latter projects is common tothe multi-storey ramped facility. It may well be neces-sary before a client commissions a detailed design for aseparate feasibility study to be undertaken in order toestablish requirements to be met for the project to beacceptable.Mixed-use structuresThere may well be situations where a multi-storey carpark is to be incorporated in a structure that will haveother uses; ancillary services, in particular the sale ofpetrol, may be envisaged, and these will pose particulardesign problems. It is necessary to consider thesematters in conjunction with the design of the car parkitself.Limitations imposed by statutory requirements andpublic policyCar-parking provision is constrained not only by re-quirements usually affecting the design, constructionand equipment of structures of this nature but may alsobe affected by national and local policies aimed at trafficregulation either through limited provision of parkingspaces, by application of the price-tariff mechanism orbyother devices. Many of these techniques are presentlybeing developed and are subject to change. It istherefore important that before embarking on anyproject the client considers current trends before enter-ing into any firm commitment.Design briefAs in the design of any structure, there must be a certainamount of dialogue between client and designer in theformative stages of the design, and the original briefmust be reviewed in the light of feedback from thedesign team. In this respect it is important to carry out afeasibility study based on a number of sketch designsthat fulfil, or as nearly as possible fulfil, the require-ments of the performance specification. Itmay then befound that the benefits arising from variation of certainitems in the original brief, such as the boundaries of thesite or the position of entrances and exits, are such as tojustify their reconsideration. The whole brief shouldthen be reviewed. Since several alternative designs mayhave to be evaluated, however, it is important to agreewith the client at the outset the criteria to be adopted forthe selection of the 'best' solution. Clearly this willoften, but not necessarily always, be on the basis of costper car space.

12Information to be considered forinclusion in the briefThe aimThe aim of the client must be stated explicitly, inparticular the purpose to which the car-park buildingwill be put. A car park can be used for a number ofseparate purposes, or a combination of them, namely: a public car park operated as a public service for profitor through a subsidy a facility for a specific development where the patternof use may be expected to remain reasonably constantthroughout the day a facility for a given activity that will generate highpeak demands at given times or lead to the assumptionthat there may otherwise be special design considera-tions.The type of vehicle for which the car park is required tocater should be mentioned if there is likely to be anyspecial requirement because of unusual vehicle dimen-sion.The siteThe brief should contain a full description of the site andits environs, with particular note of the adjacent high-way network. The status ofland at the time of writing thebrief must be disclosed, particularly any restraintsimposed by covenant or otherwise on building or access.The brief must clearly state the situation regardingstatutory consents and with whom the client expects theresponsibility for the progressing of these consents to lie.Site conditionsAll information concerning existing site conditionsshould be stated, particularly the known subsoil condi-tions including water table and drainage levels. Thearrangements for site clearance and collection of designdata relating to ground conditions should be explained.Highway accessThe purpose, layout, and present and future use of theadjacent highway network should be stated since theycan affect the viability of the project, the detailedentrance and exit arrangements and the future manage-ment policy. Attention should be drawn to any knownstreet improvements proposed, the possibility of thembeing required in consequence of the car park's con-struction, or any other matter that will affect the net sitearea available. The necessity to establish survey levels atan early stage should be emphasised. Attention shouldalso be drawn to the possibility that the street lightingunits might be conveniently incorporated in the fascia ofthe structure where it abuts a public highway.Statutory undertakersAny mains, cables, etc. within or adjacent to the site andlikely to be affected in any way by the works should bementioned.

7


9/59

Re-useFinally the client should indicate whether considerationshould be given at the design stage to the re-use of thecar park for other purposes at some time in the future.Submission of the design and costsThe client must set out the manner in which thecompleted scheme is to be submitted to him and thetime-scale that he requires. It will be for the client todescribe the manner inwhich he wiIIexpect the details ofcost to be presented to him. but the brief will necessarilyinclude all the figures in his possession to enable hiswishes to be complied with.13 Design considerationsStructuralThe brief should state: the preferred material or make clear that the choice isleft to the designer whether the structure is expected to be wholly aboveground, wholly underground or partly above and partlybelow; the final recommendations may rest with thedesigner in the light of his investigations, but anyover-riding factor affecting his choice must be stated.EnvironmentalThe client must state his wishes concerning the finishedappearance of the building, drawing attention to anyspecial circumstances known to him that will affect thefinal choice. Attention should be drawn to any require-ment to protect adjacent buildings from noise, dirt orfumes not only from vehicles but also heating, cleaningand ventilating plant.Town planningAttention should be drawn to the requirements of thelocal planning authority, and any documents already inthe client's possession should be supplied with the brief.Special planning requirements, particularly in respect ofpreservation, conservation and redevelopment shouldbe noted.Building regulationsThe client should similarly disclose any exchange ofdocuments concerning the application of the relevantbuilding regulations: he should ask for a clear explana-tion of any assumptions as to relaxation ifthe completeddesign or estimate of cost assumes that these have beenor can be obtained.14 Performance specificationGeneralIt isrecommended that the performance specification beprepared in three stages: traffic feasibility requirements site feasibility requirements accommodation and operational requirements.For car parks of less than about 200 stalls capacity thefeasibility requirements are commonly reasonably self-evident. In such instances the three stages are usuallycombined. With larger developments it is recommendedthat a feasibility study be executed to determine the

performance requirements. Large parking develop-ments and, in some instances, medium-sized parkingdevelopments may generate high traffic flows, and theneed to meet traffic requirements is of primary import-ance. In such cases it is recommended that a traffic study8

be done initially followed by a site study, the twoconstituting a feasibility study.A parking development may be associated withanother development. In such instances it may beconvenient to execute a feasibility study for the develop-ment as a whole.Certain geometric requirements are determined bythe feasibility study. In other cases the dimensions givenin Section 3 are recommended and may be regarded ascommon to all car parks; hence they are not included inthe performance specification.Traffic feasibility requirementsWhere a separate traffic feasibility study is required itshould include the external road system. The trafficstudy provides the flows required for the site study. Thetraffic study also identifies key requirements. For exam-ple in urban areas with high car-park flows the siting ofentrances and exits and their design may be critical. Thetraffic feasibility study also establishes the capacity (see(a) of Schedule below).Site feasibility requirementsAt this stage the functional design appropriate to the siteand parking requirements isprepared. This process mayinvolve preparing trial designs in accordance with theclient's brief and the traffic requirements. The perform-ance requirements determined at this stage are given in(b) and (e) of the Schedule below.Accommodation and operational requirementsTo complete the performance specification the accom-modation and operational requirements should belisted. The Schedule (points (d) to (u) below) is notnecessarily complete and indicates points that may needtaking into consideration.ScheduleThe points to be considered in the three stages are:(a) Capacity

(i) This the number of car spaces (stalls) requiredand is usually stated as a minimum capacity(ii) If part of the park is to be used for a specialcategory of user, or part of it to be partitionedas individual lock-ups, a breakdown into typesof accommodation is required(iii) The capacity is usually derived from the de-velopment that the car park serves; alterna-tively, the requirement may be to makeappropriate use of a particular site

(b) Layout(i) Floor and ramp arrangement(ii) Arrangements of entrance/exit lanes and pro-vision of reversible lanes(iii) Arrangement of control gates including thepreferredmethod of checking entry and exit(iv)Reservoir space at entry(v) Reservoir space at exit(vi) The arrangement required for pedestrian entr-ance, egress and circulation, including provi-sion for the disabled(vii) Escalators and lifts. Requirements should bespecified; any special requirement, for inst-ance for shopping trolleys, should be stated

(e) Dimensions(i) Stall size (width and length). Where there are


10/59

special requirements the appropriate stallsizes should be stated for each requirement(ii) Aisle width(iii) Clearway widths

(iv) Helical ramps:layoutminimum outer kerb radius

(d) Internal accommodation(i) Cash-kiosk requirements, includi~g _fittings(ii) Managers' office floor area and fittings(iii) Staff-room floor area and fittings(iv) Staff toilet provision required(v) Toilet accommodation required for. car-parkusers, including provision for the disabled(vi) Electricity substation requirements(vii) Storage accommodation

(e) HeadroomThe headroom is normally standard. In mixed-usebuildings the headroom should be stated for floorsnot used wholly for parking.

(f) Ramp heatingRequirements for ramp heating should be stated.(g) Entrance and exit controlsThe entrance and exit control system required, ifany, should be specified and also any paymentsystem. Where payment is to be made the auditrequirements should be specified.

(h) FinishesAny preference for finishes, including the use ofwalls for advertising purposes, should be stated.

(i) Floor finishesAny restrictions on floor finishes, for instance tofacilitate use of shopping trolleys, should be stated.

(j) Signs and floor markingsIllumination of direction signs and provision of floormarkings to facilitate circulation may be required asalso may be reference markers to enable users easilyto retrieve their vehicles.

(k) Ventilation(i) Expected rate of air change(ii) Maximum CO content permissible at anypoint in the structure.

(1 ) HeatingTemperature range to be maintained in the struc-ture, in particular the necessity for heating stair-cases.

(m) Fire fighting and preventionThe general arrangements expected with regard tosprinklers, fire points, cut-off doors and alarmsystems.

(n) Electrical equipmentMeans of protection from mechanical damage andinterference by unauthorised persons.(0) Lighting

The standard of lighting expected and the method ofcontrol required.(p) Drainage-pumps

Method of operation and control.(q) Standby power arrangements

For operation of ventilation, lighting and pumpingequipment.(r) Cleaning arrangementsThe method to be used for cleaning the car park,which will include provision for any necessary water

and power take-off points.(s) Surveillance and security arrangementsWhere these may affect detailing of structure andincluding the provision of closed-circuit television.(t) External signingRequirements for external signing should be stated.(u) Liaison

The arrangements to be made to keep the client intouch with the development of the project.Choice of solutionFinally it is essential to remember that for any givenproblem or set of criteria there is often more than onesatisfactory answer. It is clearly important that allreasonable possibilities be considered, and the client'sbrief should, therefore, not be unnecessarily restrictivebut should be broadly based to give the designer theopportunity to exercise his skill, experience and judg-ment in formulating proposals for the most effective andeconomic parking facilities.

9


11/59

2 Appearance and planning

Car parking has become a significant land use. Conse-quently, car park structures in the form of the multi-storey car park, the underground or basement car park,and the car park in a multi-function building are nowcommon. Although they are found principally in cityand town centres, they occur in many other situations,such as airports, conference centres, hotels, housingdevelopments, places of employment (both offices andfactories), places of entertainment, railway stations andsports facilities.Certain features are common to all situations. Poten-tial users should be able to identify readily a car-parkingfacility and its entrance. In urban areas it can be helpfulifa public multi-storey car park may be seen readily to bewhat it is. Multi-storey car parks are open structures topermit natural ventilation. Usually their height does notexceed about 15m. Their main structural lines arehorizontal, except for the ramped-floor layout for whichthe structural lines are inclined at a gradient notnormally exceeding 1in 20. To meet circulation require-ments it may be necessary to have external ramps.A free-standing multi-storey car park is essentially afunctional building generally composed of a series of

floors supported on columns to provide relatively largeareas of uninterrupted floor space. Very little weatherprotection is required, and there is generally no need toroof over the top floor. There is almost always greatemphasis on achieving low cost per car space, whichleads to a demand for a 'cheap' building. If requirementsdemand the use of exterior ramps, these impose con-siderable restrictions on the design and appearance. Allthese factors add up to the conclusion that the produc-tion of multi-storey car parks that are aestheticallysatisfying is almost always a challenging task.Where a car park is required as part of a development,it is generally advantageous to design the development

as a whole. By this means the circulation within thedevelopment is likely to be improved. There may thenbe the options of designing-the car park as a componentpart of a multi-function building or as a separatestructure integrated into the development. The geomet-ric design and layout recommendations in Section 3 areminima, except where clearly stated otherwise. Conse-quently, if a design for a car park as part of amulti-function building cannot be made to conform withthe recommended design minima, it is recommendedthat the car park be designed as a separate structure. Forlarge developments, and when all costs are taken intoaccount, there is no evidence that incorporating carparks in buildings with other functions increases the costof accommodating cars. Aesthetically, in some situa-tions itmay be desirable to place car parks underground,but it should be remembered that siting above groundusually reduces the cost of the structure and permits theuse of natural ventilation.10

The most difficult problems probably arise when it isnecessary to integrate a multi-storey car park amongbuildings of historic interest. These are usually built toentirely different standards of scale, and in any case theyhave very little in common with the unit - the motor car- for which the multi-storey car park is designed. Insuch circumstances a strong case can sometimes be madefor using underground car parks thus avoiding the use ofa multi-storey car park altogether. If multi-storey carparks must be provided, they can, with advantage, besmall in size, even though this may result in having agreater number of individual car parks than wouldotherwise be considered economical or desirable. It istempting to say that multi-storey car parks should beharmonized with their surrounding buildings, but thiscan rarely be done really intimately, if only because ofthe fact that much of the elevations must remain open ifthe normal methods of conforming to building regula-tions with respect to fire are to be adopted.The external appearance of a multi-storey car park is,of course, of great importance. The normal principles ofarchitectural and structural design apply however, andno special guidance need be given. It is worth notinghowever that because car parks are often not fully clad,

the structural form has a dominant influence.It is an unfortunate fact that the finish of any buildingis the first element to suffer when costs have to bepruned, and as there is generally so little marginavailable inmulti-storey car parks, this process has in thepast had disastrous results on the quality of the appear-ance. It should be strongly resisted by those responsible.The great difference in quality that exists between thebest and the worst indicates however that cost is notalways the most important factor in ensuring that asatisfactory quality of appearance is achieved. There isno substitute for skill, experience and sympathetichandling at the design stage and for good architecture.The treatment of the site surrounding a multi-storeycar park can have a considerable impact on the buildingitself, and even in urban situations there is opportunityfor hard landscaping. Intelligent choice of both hardlandscaping and planting can serve as an importantmeans of relating and connecting the car park with otherbuildings, and it is also of great value in relieving thevisual impact of the car park. Vehicle and pedestrianaccess points provide an opportunity for treatment toavoid monotony, and shrubs, trees and flowers can help,particularly at those points, and will be much appreci-ated by users. In present-day designs for urban areas,buildings are not necessarily marshalled in terraces andparades. This feature of urban planning gives scope to

set back structures from roads or streets and facilitatesthe use of external-ramp systems and the siting ofentrance and exit controls outside structures.Underground car parks pose few of the problemsoutlined above. The exception isin the ramps, which can


12/59

sterilize relatively large areas of the ground surface. Thesides of the ramps offer obvious opportunities for carefulthought and interesting treatment. However well rampsare dealt with they can never be things of beauty, andthey should, therefore, be hidden away wheneverpossible. Straight ramps are usually more difficult totreat than ones with curves. The retention of establishedtrees isimportant, and techniques exist whereby this canbe done. Attention should be paid to minimizing thenoise nuisance caused by ventilation fans in under-ground car parks.Multi-storey and underground car parks are essential-ly functional, and the scope for internal decorationtreatment is limited. In order to gain full public accept-ance however, people must be attracted to them, and a

light, airy and welcoming interior appearance helps.Much can be done by well chosen colour schemesapplied not overall, but at key positions used by driversand their passengers when they become pedestrians.Vandalism presents a perpetual hazard, and itwill rarelybe possible on grounds of cost to choose vandal-resistantsurfaces for large areas of the interior. Again, keydanger areas should receive special attention. Fullconsideration needs to be taken at the design andplanning stage of the need fully to integrate the servicesinto the structure of the car park. This includes signs andsignposting methods.Finally, it is well to remember that visitors often gaintheir first impressions of the town from a car park as thisis often the first building with which they have intimatecontact. The inferences are obvious.

11


13/59

3

3.1 IntroductionThe recommendations apply to all classes of multi-storey and underground car parks, except for those withlock-up stalls and special-purpose parks such as forstorage of cars at a manufacturer's premises. For carparks with lock-up stalls reference 1 is a useful guide.Requirements are presented in four parts: the car static requirements layout dynamic requirements.There issome latitude in the choice of dimensions, forinstance in relation to the use. This latitude may beconsidered in terms of pedestrian access to parked carsor the dynamic capacity required. Thus a greater stallwidth is recommended for short-term parking, e.g. forshoppers, than for long-term parking, e.g. for people atwork. Similarly in a small car park a low dynamiccapacity may be acceptable, since at worst relatively fewdrivers will be inconvenienced and then only for a shortperiod. In a large car park such a restraint may beunacceptable because of the larger number of driversaffected and the greater overall delay that would becaused.The cost of providing car-parking space in multi-storey and underground car parks is not inconsiderable.In the circumstances it may be appropriate to considerwhether in a particular case lower design standards thanthose recommended may be adopted. Particularly forprivate car parks it is sometimes suggested that smallerstalls may be used and that lack of circulation capacitycan be overcome by controlling the circulation and theparking of cars. Ithas been found that in the general casecar size isnot directly connected with the income level ofowners. Large cars may be bought relatively cheaplysecondhand. Control measures can be considered, butapart from control by altering entrances and exists inuse, such measures have not usually been found prac-tical.A distinction has sometimes been made betweendriver parking and attendant parking on the ground thatwith attendant parking lower geometric standards maybe used, but these standards are not considered. Atten-dant parking is, perhaps, less attractive at present,because of its relatively high operating costs and lowdynamic capacity.It is recommended that provisions be made forentrance and exit controls from the inception of plan-ning of a car park. In some instances no controls arerequired. In many instances, both for public and privatecar parks, entrance and exit controls are required torestrict use to those authorised, to exclude cars when thecar park is full, to prevent cars entering by an exit, or toensure that payment for use is made. Itis recommendedthat provision be made and that it should permit thevarious types of control being installed since in the12

Design geometry

course of time it may be necessary to install controlswhere none is required initially, or to alter the controlsinstalled as a consequence of changing circumstances. Ifprovision isnot made for entrance and exit controls fromthe inception of planning it may be difficult or impos-sible to make adequate provision at a later date withinthe site area.Recommended dimensions in this Section are net, andallowances should be added for finishes and fittings. Forstalls demarcated by lines on floors, dimensions are tothe centres of lines.3.2 The carThree design cars are used for car park design purposes;the small car; the standard car; the large car. Thedimensions of these design cars are given in Table 1.The swept area on a turn is shown for the large car inFig. 1.The large car used in Fig. 1isthe large car used forhighway design.?Recommended practice is to design for normal use bythe standard car and for occasional use by the large car.The design car dimensions in Table 1 were obtainedfrom a statistical analysis of new car registrations in1971. It was found that 95% of new car registrationsfitted within a rectangle on plan of 4.750m x 1.800m.The 5% of cars larger than the standard car fitted with arectangle on plan of 6. 100m x 2.00m. The small car wasrepresentative of 50% of new car registrations. Sincethese dimensions for design cars were established thesizes of cars will have changed. Investigations from timeto time have indicated that any such changes in thedimensions of cars are insufficient to justify altering thedesign standards for car parks. The design cars describedin Table 1and in Fig. 1are in current use for the design oflocal authority housing schemes and for the design ofhighways.Table 1 Comparative table of design car sizes1proportion length width turning-circle diameterof new on onregistrations plan plan between betweenm m kerbs, m walls, mlarge car 100% 6.100 2.000 15.000 -standard car 95% 4.750 1.800 13.000 14.000small car 50% 4.100 1.600 11.000 -No height is specified for the large car. From anexamination of lists of new cars available in the UnitedKingdom the maximum height was found to be 1.829mexclusive of roof rack and radio aerial. The majority ofcars have an appreciably lesser height.The design car dimensions given in Table 1and Fig. 1apply to cars registered in the United Kingdom whethermade in the country or imported. The dimensions arenot representative of the North American car.It may be necessary to design for the North American


14/59

car. The dimensions of the United States of Americadesign vehicle" are:lengthwidthwheelbasefront overhangbetween axlesrear overhangturning circle (diameter)outer wall

5.72m2.03m1.05m3.23m1.55m14.94m

These dimensions were published in 1973 and aredefined as the 'dimensions equal to or greater than thelargest common models likely to frequent a parkingfacility." The maximum height is commonly 1.600.4The recommended dimensional requirements for theNorth American car" are dimensions in feet convertedinto metres. In practice one would not expect dimen-sions inmetres to be the exact equivalents of dimensionsin feet. Depending on the unit of measurement, feet ormetres, the practice is to round off to a convenientnumber taking into account the degree of precisionjustified in each instance. The dimensions given herehave not been rounded off.r>.,\f;; j

~'";1l

-,\\, \.__ .---L-.

1. Swept area of large car (highway design)2

3.3 Static requirementsStall width, stall length, aisle width and bin widthThe bin width is a function of the stall length, the aislewidth and parking angle.Recommended stall dimensions (UK) are:stall lengthstall widthlong staygeneralshort staydisabled persons+"minimum 3.200mpreferred minimum 3.600mThe stall width for disabled persons is inclusive ofwheelchair users. For the architectural provisions to beincorporated in a building to make it convenient for useby disabled people reference should be made to BS5810.7For the North American car the recommended stalldimensions are:"

4.750m2.300m2.400m2.500m

stall length 5.639mstall widthindustrial, office employees 2.591mpublic, residential 2.743msupermarket 2.896m to 3.048mA width of 2.743 is acceptable for most uses.

Recommended aisle and bin widths are given inTables 2a and 2b.Table 2a Recommended aisle and bin widths - UKparking aisle width bin widthangle (stall length 4.750m)minimum preferred stall minimum preferredm m width m minimumm m

two-way aisle90 6.9S0 r 6.950 all 16.450 16.450one-way aisle90 6.000 6.000 all 15.500 15.500

80 5.250 5.2S0 2.3UO 15.404 15.4042.4UO IS.439 IS.4392.500 15.474 IS.47470 4.500 4.700 2.300 IS.000 IS.2002.4UO 15.069 15.2692.500 IS.137 15.33760 3.750 4.200 2.300 14.277 14.7272.400 14.377 14.8272.500 14.477 14.92750 3.500 3.800 2.300 13.734 14.()342.4UO 13.863 14.1632.SOO 13.991 14.29145 3.500 3.60() 2.3UO 13.470 13.5702.400 13.612 13.7122.500 13.752 13.853

The bin width is for an aisle with a stall on each side.Parking angles of less than 90 are little used inunderground and multi-storey car parks. Hence forthese parking angles the aisle widths are provided forguidance and circumstances may justify using differentwidths.For the North American car the recommended aisleand bin widths are given in Table 2b.Table 2b Recommended aisle and bin widths'' - USA

parking angle aisle width bin widthm m90 7.925 19.2027So 7.010 18.89860 4.877 16.45945 3.658 14.326Notes:I.Stall width 2.743m. A bin is an aisle with a stall on either side.2. These dimensions are for 5.639m long stall, measured parallel tovehicle, and are based on results of a special study to evaluate theeffects of varied aisle and stall width for the different parking anglesshown. The study was conducted in December 1970 by the FederalHighway Administration and Paul C. Box and Associates.

Side clearance on structureWhere a stall is adjacent to a large element such as a wallit is recommended that a clearance of 0.230m beprovided.ColumnsRecommended distances from the aisle are:

minimumpreferred minimum 0.460m0.800 to 1.000mWhere columns are set back the recommended dis-tance from an aisle they may encroach on the stall width.

If columns are set nearer to the aisle the effect is toreduce the stall width. Clear-span construction isprefer-red, but financial considerations often lead to the use of13


15/59

columns. Ifcolumns are used it is recommended there benot less than three stalls between columns.Height!,he recommended minimum clear height or headroomIS 2.050m through the building. Vehicles of the motor-caravan type are considerably higher than the generalrun of cars and may need to be accommodated forinstance in a residential area. This may be done by givingthe ground floor the higher minimum headroom of2.3


16/59

2300 1-520 23002150

r>.Ifsuitablestraightaccesswayavailablebeforeinstallation

Centre-line1-220 of kiosk windowClosing In -~.- .- CO). .-loop ~\ 0 NN Kiosk Flexible /~ bollards ~.-.- '--1 _" \IOV 0Photoelectric0 a>In Vcell N Nt:'I Barrierp~------- - arm,Barrier' 0 0arm N~Detector 0a> It-.'___ - -_:jj--'loop InN Closin~ loop

-11-,-,- .- ~I. k t . . ,-TICe -ISSUingmachine

\r ~In Out

0.2J01 ...1---2-.5--2-5-----I~ I . . .---2-.5-2-5--~~1 10.230Plan

Ticket-issuingmachineTicket-isSUing"leveL I

Section A-A2. Layout of entrance and exit controls (pay on exit)Notes: (i) 6000m of straight accessway is desirable at theapproach to kiosks and ticket machines(ii) The headroom should be displayed at the entrance.This may be done by placing a bar over each entrance laneat the headroom height with the headroom marked on it.The maximum permitted width of road vehicles isordinarily 2500m. Hence there may be a demand toprovide a width of, say, 2600m at entry and exit controlpoints. If such a width is provided at automatic ticket-issuing or payment machines the dynamic capacity of theequipment will fall as, for instance, some drivers may

find it necesary to leave their cars to use the machines. Ifit isconsidered necessary to provide a greater width thanis required for cars it is recommended that temporarymeasures be provided to reduce the width when theentry or exit is used by cars only.

The height of ticket-issuing machines and window-silllevel of the kiosk should not exceed 1150m to reduce asfar as possible difficulties met with while taking ticketsand paying parking fees when seated in a car.It is recommended that a straight accessway of at least6000m length be provided on the approach to aticket-issuing machine or a payment kiosk.It is desirable to provide an area of the least possibleslope at control points to reduce braking and startingdifficulties. A maximum gradient of 1 in 40 is desirable,but gradients of up to 1in 12 have proved acceptable, ifnot desirable.Between the public road system and entrance and exitcontrol barriers vehicle reservoirs are required (seesubsection 3.5).Where an unattended automatic control isprovided atan entrance or exit it is necessary to provide for systemmalfunction. The control equipment may malfunctionor drivers may be unable to operate the system. Forexample when a car stops the engine may stop and thedriver be unable to restart. Alternatively a driver may beunable to open the exit control because the pass, token

or money required is not to hand.At an exit with an unattended automatic control alayby should be provided inside the car park at the exit.Cars unable to leave the car park may then be put in thelayby leaving the exit clear for following cars.Where unattended automatic equipment is installedat an entrance or exit the layout may require enlarging topermit some duplication of equipment to allow formalfunctioning. Requirements will depend on indi-vidual circumstances, including the provision made bymanufacturers in equipment to reduce malfunctioning.3.4 Layout ofcar parksPrinciplesThe design details of car parks are, in general, indepen-dent of their size. Three considerations affect the layoutsof larger car parks: both the static capacity and the dynamic capacity mustbe adequate search paths for incoming drivers should not involvemore than about 500 stalls the maximum number of floors or circuits to besearched for a stall is often regarded as six; a greaternumber of floors may be frustrating because of delaysto drivers and disorientation may result from thelarger number of turns and ramps involved. It followsthat if entrances are provided to more than one level,or if accessway ramps climbing two or more floors areused, then more than six floors or circuits may befeasible.Car parks expected to carry considerable traffic flowsthroughout the day should preferably have one-way-only systems. This applies also to industrial car parks forshift workers' cars. It does not apply so strongly to carparks for day-only office or factory workers where theremay be demands only for maximum inflow and zerooutflow, or vice versa.Multi-storey and underground car parks are laid outusing the same principles as apply to surface car parks.With existing public car parks it may be impractical toachieve 100% stall occupancy. Itisusual to provide a car

park with an automatic counting mechanism that main-tains a total of the cars in the car park. This mechanism isused to operate a sign showing 'parking' or 'full' at theentrance. The operator may find it necessary to set thismechanism to show 'full' when the number of cars in the15


17/59

car park is less than the number of stalls but congestion isbeing experienced.

It is not practical at the entrance to a car park toallocate particular vacant stalls to drivers and to enforceuse of stalls so allocated. The onus rests on drivers tosearch for vacant stalls. This search is facilitated bylaying out a car park in units. At the entrance and exit ofeach unit an automatic counting mechanism is thenprovided that maintains a total of the number of cars inthe unit. This counting mechanism is then used tooperate a sign showing 'space' or 'full' at the entrance tothe unit. This tells drivers if they will find a vacant stall ina unit.Drivers entering a car park or unit of a car park do not

necessarily park in the first vacant stall they come to.Hence the circulation of a car park, or unit of a car park,should permit a search being initiated for a vacant stallfrom anywhere in the car park, or unit of the car parkwithout leaving the car park or unit.While stalls may be reserved in multi-storey andunderground car parks it is not the practice to install anyenforcement mechanism such as barriers. In largecentres of employment many may require parkingspace, but commonly appreciably fewer are present atanyone time owing to absences for a variety of reasons.When preparing the layout of a car park it is usual to

refer to designs of existing car parks. Public multi-storeyand underground car parks commonly are under used;there are exceptions of course. When a large publicmulti-storey car park in a town or city centre is visited itis quite usual to find most of the cars parked on floorsnear pedestrian exits. On other floors there may befewer cars and the roof level may be empty. Conse-quently reports on the convenience of car parks bydrivers and operators may not be informative. Publishedinformation on car parks that have been built does not asa rule include an operational assessment. Hence whenusing existing designs for guidance it is recommendedthat designers first make their own assessment ofoperational suitability.Cul-de-sac parkingIt is preferable to avoid using multiple cul-de-sac aisles.If they are used the capacity of a cul-de-sac should belimited to about 6 stalls.Cul-de-sacs are difficult to manoeuvre in and neces-sarily lie off a driver's search path for a vacant stall.

One- and two-way aislesThe advantages and disadvantages of one- and two-wayaisles are set out in Table 3.Parking angleIn one-way aisle systems placing stalls at an angle of lessthan 90 to aisles for forward parking is a conveniencefor drivers since it facilitates driving into and reversingout of stalls. A disadvantage of using a lesser parkingangle is that a greater floor area per car is required. Thisdisadvantage may be expressed as a reduction in thestatic efficiency, namely the ratio of the area provided installs to the total considered floor area, expressed as apercentage. Static efficiencies for various parking anglesand for a parking area without columns are:parking angle bin width static efficiency90 15500m 613%

80 15439m 606%70 15269m 585%4SO 13712m 490%

stall length 4750mstall width 2400m16

Reducing the parking angle increases the dynamiccapacity of the aisle. Reducing the parking angle from90 to 80 has a relatively marked effect; reducing theparking angle further has relatively little further effect.Layout controlsThe layout of a car park is determined by the staticcapacity required, the site dimensions, the traffic de-mand (dynamic capacity required), the access to the siteand the entrance and exit control requirements. Thelayouts of entrances and exits may also be affected bytraffic flows on the road system. There may also be arequirement to combine the car park in a building withother uses. In consequence, a comparison of alternativelayouts in terms of their geometry alone is incomplete.For the purpose of arriving at a satisfactory layout itmay be useful to use the concept of efficiency. The staticefficiency is the ratio of the area provided in stalls to thetotal considered floor area, expressed as a percentage.Achieving maximum structural efficiency involves mini-mizing the structure cost per stall. These measures ofefficiency do not necessarily give the same result andmay not give the best functional efficiency.Table 3 Functional comparison of aisleso ne -wa y a is le s

Easily understood system andrequires little discipline

t wo -wa y a is le sDynamic capacity good,especially when angleparking isadopted. Aislewidths may be less thantwo-way aisles

Dynamic capacity normallyless than one-way aisles, butmay be greater ifmaximumcontraflows do not occursimultaneously so thatadvantage of the greaterwidth of the two-way aisle canbetaken

Ifnarrow one-way aisles areadopted, vehicles straddlingstall/aisle demarcation linescan obstruct the aisle

Generally greater width ofaisles has lesser effect on aisleobstruction

Higher stuctural efficiency Lower structural efficiencyDisregard of one-way trafficdirections not uncommon inpublic car parks resulting indisruption of flow and createsaccident hazardParking-area layoutParking area layouts may be classed as:

flat decksplit levelramped floor andwarped slab

All classes are commonly built with up to six levels,that is for a multi-storey car park, a ground level and upto five levels above ground. The principles of layouts arereviewed here.The flat-deck layout is illustrated in Fig. 3. Each deckis flat. The decks are linked by ramps. In the illustrationexternal curved ramps are shown. Straight ramps may beused in which case usually they are sited internally. Withthe ramp arrangement in Fig. 3 it is possible to installautomatic counters at each deck to operate a signshowing 'space' or 'full' as an aid to drivers. Flat-deckcar parks usually are built in multiples of a bin in width,


18/59

3. Flat deck car park witb external ramps

4. Split-level car park witb combined entry and departurecirculation and witb end ramps

5. Split-level car park witb separate entry, and departurecirculation and a sbort down (departure) ramp system

6. Split-level car park witb separate entry and departurecirculation and witb sbort up (entry) and down(departure)ramp system

but the layout is adaptable to a site. In Fig. 3 the rampcirculation is anticlockwise to suit the entrance and exitarrangements. In the United Kingdom a clockwisecirculation is preferred, that is with the driver on theinside of the turn. This is not regarded as essential.The split-level layout is illustrated in Figs. 4,5 and 6.

The illustrations are of multi-storey car parks, that isdrivers enter by the up-ramp system and leave by thedown-ramp system. In an underground car park thesame principles apply but the ramps reverse; the down-ramp system becomes the entry-ramp system. Theparking levels are flat decks or levels. The rise betweenlevels is half the floor to floor height. Since the risebetween levels is usually 1.500m or less the ramps maybe at 1 in 7. This class of car park is commonly built withup to 12 levels inclusive of the ground levels. It is usualfor aisles to be one way since they are part of the rampcirculation which is one way. The levels usually are a binor multiples of a bin in width but may be adapted to asite.In Fig. 4 the up-and-down ramps are at the ends of the

structure. The scissor arrangement of the up-and-downramps has a low dynamic capacity since sight distancesare short where traffic streams merge. As shown in Fig. 4the departure route is long. In Fig. 5 the up-and-downramp systems have been separated. The down-rampsystem is short, and the up or entry-ramp system inprinciple includes the remaining stalls. Fig. 6 illustratesthe use of a short up-en try-ramp system as well as a shortdown-ramp system.Attractions of the split-level layout are its compact-ness, that the ramp system is internal and that the space

taken up by the ramps is a minimum. It may be difficultto search systematically for a vacant stall. In car parkslaid out on the lines of Figs. 5 and 6 a driver may see avacant stall that cannot be reached, if the one-way aislesystem is observed, without first going up a level andthen down a level. Similarly, when leaving from somestalls it is necessary first to go up a level.The ramped floor layout is illustrated in Figs. 7, 8 and9. Cars are parked off an aisle, which also acts as a ramp.

The ramp may be two way. Fig. 7 shows a one-way aislesystem with a clearway down (departure) ramp. Sincethere is a single search path this layout is not recom-mended for a car park capacity of more than 500 stalls.Even then the search path may be found inconvenientlylong. Instead of a clearway departure ramp a departureparking ramp may be used. In Fig. 8 the down parkingramp is end to end with the up parking ramp. In Fig. 9the up-and-down parking ramps are interlaced. Theview has been exploded to show all ramps. Rampedfloor car parks usually are built two bins in width, andthe layout is not adaptable to a site. The ramp need notbe laid out as in the illustrations. Itmay for instance belaid out as an oval or a square. In a ramped-floor carpark with a steep gradient it may be found difficult toopen or hold open a car door on the up gradient side andto close a door on the down gradient side.The warped-slab layout is illustrated in Fig. 10. At the

edges the floor slabs are flat. Internally the floors arebuilt to falls to provide an internal ramp system. It isusual for aisles to be one way. The layout is adaptable toa site in the same way as the flat deck layout. A factorthat should be considered with the warped-slab layout isthat the maximum gradient occurs on the centralcrossover. If a car is parked in this area it may be difficultto open or hold open a car door on the up-gradient sideand to close a door on the down-gradient side.

17


19/59

RampsRamps are required to give access to parking levels. In acar park with three or more parking levels, access tothose levels may involve the use of aisles (as is the casewith split-level car parks), or the layout may not requiredrivers to route through aisles. A clearway ramp is aramp system that does not include aisles. Ramps may bestraight (which term includes ramps with bends) orhelical (circular in plan).Clearway ramps are used when it isdesired to improveaccess time, or to avoid through traffic in parking areas,or where a ramp aisle system has insufficient dynamiccapacity. If only one c1earway ramp is provided it isusually the departure ramp.Two-way ramps require to be designed substantiallyto highway layout standard, in particular with regard tosight distance and lateral proximity of structure. Failureto design to an adequate standard will result in areduction in capacity and may introduce an accidentrisk. Where requirements cannot be met it is recom-mended that a two-way ramp be designed as twoone-way ramps with segregation of the traffic streams by

barrier or kerb.In some layouts contraflow occurs on straight rampsor crossovers between ramps. To avoid traffic streamscrossing drivers are required to drive on the right insteadof keeping to the left as is required on public roads. Insuch instances it isrecommended that the traffic streamsbe separated by a kerb or barrier. A barrier may extendbeyond the ends of a ramp or crossover to discouragedrivers from attempting to drive in the wrong lane.The use of a helical ramp is illustrated in Fig. 7.Usually a helical ramp is sited externally but may beinternal. The recommended direction of flow in theUnited Kingdom is clockwise, that is with the driver onthe inside of the turn. This is recommended for ramps ofminimum radius. If a larger radius is used an anticlock-wise direction of flow is acceptable; ramps are in usewith an anticlockwise direction of flow.For car parks outside of the United Kingdom thepreferred direction of circulation is with the driver onthe inside of the turn.Concentric helical up-and-down ramps may be used inlarger car parks. The up-and-down ramps serve alter-nate floors respectively. In such instances the outerramp should be the up ramp as it will have the lessergradient.Entrances and exitsThe geometric layout requirements for entrance and exitcontrols are illustrated in Fig. 2. Between the externalroad or street and an entrance or exit barrier a vehiclereservoir is required (see subsection 3.5). Control isfacilitated by having the minimum number of entranceand exit points. Where payment isto be made on exit it isdesirable for the layout to permit all exits to be closedexcept one. This will enable the car park to be operatedby one cashier at times when the demand is low.It may also be advantageous to site the entrance andexit side by side, with one or more lanes made reversi-ble. If then a peak inbound demand occurs at a differenttime of day from a peak outbound demand a lane orlanes may be made reversible and to operate to serve thepeak demand. With a pay-at-exit system having theentrance beside the exit enables the cashier to exercisesurveillance; alternatively surveillance may be byclosed-circuit television.Between an entrance control and the public road or18

7. Ramped-floor car park with a clearway down (departure)ramp

8. Ramped-floor car park with separate entry and departureparking ramps

9. Ramped-floor car park with interlaced entry and departureparking ramps (exploded view)

10. Warped-slab car park


20/59

street a reservoir is required to avoid cars queuing on theroad or street. The layout should permit cars in thereservoir returning to the public road system withoutentering the car park.Where the use of a car park is controlled by the tariff(for example, a high charge may apply to a long stay in acar park intended for short-period use), the tariff or theintended use of the car park should be advertised. Thisshould be done in such a way that drivers may see whatthey are committed to before entering.Choice of layoutThe factors affecting the layout of a car park, to whichreference ismade in Section 1, are so many and variableit is not practical to propose ideal layouts. It is recom-mended that the predominant use to which the car parkwill be put be borne in mind. The duration of parkingvaries with the trip purpose. Itmay be less than one hourfor shopping consumables. For business trips the dura-tion of parking isusually longer; it isstill longer for worktrips. For park-and-ride (for example at a railway stationor airport for short-haul travel), the facility to parkwithout delay is important.The recommended maximum search path of 500 stallsinprinciple limits layouts with internal ramp systems to amaximum of 500 stalls capacity. This limitation arisessince in general car parks with internal ramp systems arenot equipped with automatic vehicle counters to operatesigns informing drivers which parts of the car park arefull and where there is space. Car parks with internalramp systems have been built of substantially greatercapacity than 500 stalls, but as previously mentioned,public car parks are commonly used at well below theirdesign capacities in terms of stalls. If the attempt ismadeto use such a car park at near its capacity in stalls delayshould be expected. This will act as a deterrent to theshort duration parker or to park-and-ride travellers.The search path of 500 stalls isthe absolute maximum.The preferred maximum is about 200 stalls, i.e. car parksofmore than 200 stalls preferably should have more thanone search path.For larger car parks the preferred layout is usually theflat deck with external ramps. The ramps may bec1earwaywhen usually they are helical. An alternative isthe curved ramp illustrated in Fig. 3. This layout can bedesigned to include automatic vehicle counters thatoperate signs to inform drivers at each deck if it is full orthere is space.3.5 Dynamic requirementsProcedureThe design procedure is to estimate the traffic demandsand the dynamic capacities for the various parts of a carpark. The two are then brought into balance by adjust-ing the layout or the details of the design. The turnoveradequacy should then be checked.Traffic demandThe vehicular traffic demand may be expressed in carsper hour. For a car park as a whole the minimuminformation required is:for each entrancethe traffic demand for the car park peak hourfor each exittraffic demands for the car park peak hourstraffic demands for the highway peak hourstraffic flows on the road or street for the car parkpeak hours

traffic flows on the road or street for the highwaypeak hoursThe precision with which traffic demands need beestimated may be assessed from the dynamic capacitiesof the parts of car parks. When determining the trafficflows on roads or streets it may be appropriate to allowfor change of flow with time.It isusual to consider the traffic demand as dependent

on the journey purpose of the journey served. Whereinformation is not available on the journey purpose acommon practice is to allow for a demand equal toone-quarter of the car park capacity arriving or leavingin '/4 hour.Dynamic capacityThe data on dynamic capacity have been obtained fromreference 8 except where indicated. The dimensions ofthe aisles, stalls and cars used to establish the data are:

aisle width 4.877 and 7.315mstall width 2.286 and 2.743mstall length 4.877 and 5.486mcars, maximum dimensionslength 4.780mwidth 1.800mturning circle between kerbs 12.500m

The data are necessarily of a limited nature. It isrecommended that consideration be given whether thecircumstances of a car park may justify some modifica-tion of the dynamic design capacities proposed. Thevariables used in formulas below are:C cars per houre n cars per hour inwardCaUl cars per hour outwardXI aisle width, metresX2 stall width, metresX3 stall length, metresX4 percentage of cars reversing into stallsX5 0 for one-way aisle; Ifor cul-de-sac aisleA area per car space, square metres(=X2(2XI+ XI )/2)N number of lanes in road or streetr radius of curvature of vehicle path, metresS saturation flow (vehicles per hour) in nearside lane of road or streetW ramp or accessway width (metres),3.000m or greaterWI carriageway width of road or street,metres

Vehicle speedThe dynamic capacities of the parts of car parks arelargely independent of the speeds of cars. Provided thatfree-flowing conditions prevail, the driver obtains littlebenefit from increased speeds.Capacities of aisles and stallsThe capacity of an aisle with 90 parking is given by theformulas:

Cin = 55X,+425X2+150X3-1O.24X4-849alsoCin = 49A-1O.IX4+300COUI = 66X, +242X2+ 52X3 +7.7X4-136Xs-690

alsoCOUI = 34Ax7.5X4-109Xs-90The formulas apply to straight and zig-zag aisles. Thecoefficient of X3 in the formula for the outflow capacityis not statistically significant.

19


21/59

Inflow capacrties with 90% confidence limits areplotted in Fig. n. Outflow capacities with 90% confi-dence limits are plotted in Fig. 12.The formulas apply tocul-de-sac and one-way traffic systems, with no carsunparking during inflow periods, and vice versa. Capac-ity is independent of aisle length. For estimating thecapacity of a system the allowance for cars reversing topark may be taken as 30% for 900 parking.'600r----.----~----_.----,_----._--_.

Inflow30", reversedin stalls

>.. . . .uoQ.ou

1-'000eu

~o. . . .c-200 90'"confidence limits ----

Area per car space11. Inflow capacitySource is RRL report LR221812. Outflow capacitySource is RRL report LR 2218'600r----.----~-----.----~----.----.

Outflow30", reversedin stallsOne-way-only aisle

_ ---- -_ -_ -- - - -_ - - -_ _

90",confidence limits - - --

Area per car space20

Calculated capacities of aisles are:stall width aisle width cars per hourin out870 750910 760950 790

m m2.300 6.1002.400 6.0002.500 6.000Assumed: stall length 4.750m30% reversing into stallsone-way aisle, stalls on both sides900 parking

Time taken to park, and stall widthFor stalls of width 2.300 to 2.750m, the average time topark is reduced by 20 seconds to 33 second per metreincrease in stall width depending on whether the carpark is empty or full, respectively.Parking angleThe angling of stalls adjoining one-way aisles reducedthe percentage of drivers reversing to park (and henceincreases the dynamic capacity of the aisle).Proposed allowances for reversing to park are:

stall angle approximate proposedproportional allowance forchange in drivers drivers reversingreversing into into stallsstalls1.000.430.400.37

30%13%12%11%Ramp capacityThe recommended capacity of a straight ramp is 1900cars per hour. (The evaluation was made on 3.048mramps at a gradient of 1 in 13 or 7.7%.) The capacity isthe same for up and down ramps. For the rampsevaluated the speed obtaining did not affect capacitysignificantly.Accessway and carriageway capacityThe capacity of straight accessways and carriageways isgiven by the formula:

C=15W+1800.The formula applies to one-way accessways andcarriageways of widths 3.048 to 9.144m.For a 3.000m accessway the calculated capacity is, say,1850 cars per hour. The formula applies to accesswayswhere drivers do not overtake or travel side-by-side.Where overtaking or driving side-by-side occurs thecapacity formula for public roads applies: C=525WI

Bends on accessways and rampsThe capacity of bends on accessways and ramps is givenby the formula:C= 1850/(1+100/,-3).

This formula applies to helical ramps. A helical rampof outer kerb radius 12.000m and width 3.65Om has acalculated capacity of about 1700 cars per hour.Entrance-barrier capacityThe recommended capacity for a left-hand turn-inwhere the ticket is taken from a machine is 450 cars perhour. Proprietary equipment is normally used for entr-ance barriers that may have a higher dynamic capacity.


22/59

Vehicle reservoir at entrance, and entrance layoutThe short-period arrival rate of cars may exceed theentrance barrier capacity (and/or the dynamic capacityof other parts of a car park). To prevent a queueextending on to a public road a vehicle reservoir may beprovided.In a situation where drivers may have to wait to enter acar park because it is full, it is desirable to have a layoutsuch that a driver in an entrance reservoir may return tothe street or road without entering the car park.Exit-barrier capacityThe recommended capacity is:Pay on exit to attendant:attendant calculates thechargefixed chargeDriver purchases token beforeleaving car park and at the exitinserts token into a machine

200 cars per hour270 cars per hour

400 cars per hourThe capacity of attendant systems is low in compari-son with the traffic demands commonly experienced inlarger car parks. Consequently, there is a demand forsystems with a higher capacity, and proprietary systemsare under development. Hence it is recommended thatthe availability of proprietary systems with a highercapacity be considered when preparing a design.The pay-on-exit capacity of 200 cars per hour wherethe attendant calculates the charge may not be achieved.Drivers often experience a slower rate. The rate wasdetermined for town and city-centre car parks whenpayment commonly was in coin. Observed rates were inthe range 150 to 225 cars per hour. To achieve a high ratethere must be an adequate vehicle reservoir between thebarrier and the outside road or street. The cashier's

kiosk should be designed for ease of access to drivers.The kiosk needs to be equipped for the rapid calculationof the charge. The cashier needs to be trained. Also atrained cashier will require relieving if a high rate has tobe maintained over a long period. Where payment ismade and change is given in notes it is considered that arate of 200 cars per hour is unlikely to be obtainable andthat a lower rate will have to be estimated.For a large car park a low exit-barrier capacityassociated with a pay-on-exit system results in many exitlanes being required most of which will be required onlyinpeak periods. Space will also be required for drivers todiverge to vacant exit lanes. In such cases it issuggesteduse of an alternative system be considered such as thepay-on-foot system. In this system drivers pay to acashier or machine before going to their cars and receivea ticket or token. At the exit the ticket or token isinserted in a machine to open the exit barrier.Exit capacityThe exit of a car park on to a road may be evaluated as aT-junction. The exit is the minor road or stem of the T.The road.is the major.or bar of the T. Where the majorroad carnes zero traffic the recommended capacity of acar-park exit is:turning left, no possibilityof other traffic estimate asfor anaccessway with bendturning left withrestricted sight line,GIVE WAY signorWAIT sign and stop line say, 780 cars per hour

For the case where the major road carries traffic themethod of assessment is illustrated by an example.Given:car park exit (minor road)traffic demandexit accessway capacityroad (major road)one-way with two lanescarriageway width (WI)through traffic

200 cars per hour780 cars per hour6 . 100m800 vehicles per hour

Calculation:estimate the saturation flow on road (major road)near side laneS=525WIINS=525x6.1xl/2=1600 vehicles per hourminor road (car-park exit)saturation flowtraffic demandmajor road (public road)saturation flow in near 1600 vehicles per hourside lane without carparktraffic demand

780 cars per hour200 cars per hour

400 vehicles per hourEnter Table 4 with data for the minor road and majorroad.The minor road exit capacity is about 530 cars perhour.Evaluation:The exit traffic demand of 200 cars per hour is wellwithin the capacity of 530 cars per hour.

Table 4 is for major roads with a near side-lanesaturation flow of 1600 vehicles per hour; Table 5 is for2000 vehicles per hour. Both Tables apply to a singlestream of left-turning cars entering a single lane oftrafficina one-way road. Additional traffic inother lanes ofthemajor road is ignored. Tables 4 and 5 are calculated onthe basis that for a car to leave the car park exit theremust be a gap of 5.4 seconds in the road traffic.The example is for a left turn out of a car park. Forright turns reference 2 may be consulted for guidance.Where the external road carries a significant traffic flowit may not be feasible to provide for a right turn out froma car park using a priority-type junction.

Vehicle reservoir at exitF~r an exit barrier to operate at its design capacity adnver must be able to draw clear immediately thebarrier opens. If then cars have to wait to enter the roada queue may form and obstruct the barrier to such anextent as to cause an unacceptable reduction in capacity.In these circumstances a vehicle reservoir is requiredbetween the exit barrier or barriers and the road.Requirements for exit-vehicle reservoirs may be esti-mated using Figs. 13, 14, 15, 16,17 & 18 which apply toexit-barrier capacities of 200,270 and 400 cars per hour.The design method is illustrated by an example."Given:car-park peak departuredemand 700 cars per hourexit-barrier capacity(one barrier) 270 cars per hourexit is on to a one-way street;flow on near side lane 500 vehicles per hour

21


23/59

Table 4 Capacity (vehicle/h) of minor-road for left-turning traffic at T-junction, where saturation flow for near-side lane is 1600vehiclelh8Acceptable gap in major-road traffic = 5.4 seconds

f l o w i n s a t u r a t i o nf l o w f o r m i n o r - r o a d ( c a r / h )N / S l a n e( v e h i c l e / h ) 7 0 0 8 0 0 9 0 0 1 0 0 0 1 1 0 0 1 2 0 0 1 3 0 0 1 4 0 0 1 5 0 0 1 6 0 0 1 7 0 0 1 8 0 01 0 0 6 4 5 7 3 1 8 1 6 9 0 2 9 8 8 1 0 7 4 1 1 6 0 1 2 4 5 1 3 3 1 1 4 1 7 1 5 0 3 1 5 8 92 0 0 5 9 1 6 6 4 7 3 7 8 1 0 8 8 3 9 5 6 1 0 3 0 1 1 0 3 1 1 7 6 1 2 5 0 1 3 2 3 1 3 9 63 0 0 5 3 7 5 9 9 6 6 1 7 2 3 7 8 5 8 4 7 9 0 9 9 7 1 1 0 3 4 1 0 9 6 1 5 1 8 1 2 2 14 0 0 4 8 5 5 3 7 5 8 9 6 4 1 6 9 3 7 4 5 7 9 8 8 5 0 9 0 3 9 5 5 1 0 0 8 1 0 6 05 0 0 4 3 4 4 7 7 5 2 0 5 6 4 6 0 7 6 5 1 6 9 5 7 3 8 7 8 2 8 2 6 8 7 1 9 1 56 0 0 3 8 5 4 2 0 4 5 5 4 9 1 5 2 7 5 6 3 6 0 0 6 3 6 6 7 2 7 0 9 7 4 5 7 8 27 0 0 3 3 7 3 6 5 3 9 4 4 2 3 4 5 3 4 8 2 5 1 2 5 4 2 5 7 2 6 0 2 6 3 2 6 6 28 0 0 2 9 1 3 1 4 3 3 7 3 6 0 3 8 4 4 0 8 4 3 2 4 5 6 4 8 0 5 0 4 5 2 9 5 5 39 0 0 2 4 7 2 6 5 2 8 3 3 0 1 3 2 0 3 3 9 3 5 9 3 7 7 3 9 7 4 1 6 4 3 5 4 5 51 0 0 0 2 0 5 2 1 9 2 3 3 2 4 7 2 6 1 2 7 6 2 9 1 3 0 6 3 2 1 3 3 6 3 5 1 3 6 61 1 0 0 1 6 5 1 7 5 1 8 6 1 9 6 2 0 7 2 1 8 2 2 9 2 4 1 2 5 2 2 6 4 2 7 5 2 8 71 2 0 0 1 2 8 1 3 5 1 4 2 1 5 0 1 5 8 1 6 6 1 7 4 1 8 2 1 9 0 1 9 8 2 0 7 2 1 31 3 0 0 9 2 9 7 1 0 2 1 0 7 1 1 2 1 1 8 1 2 3 1 2 9 1 3 4 1 4 0 1 4 6 1 5 11 4 0 0 5 9 6 2 6 5 6 8 7 1 7 4 7 7 8 1 8 4 8 8 9 1 9 51 5 0 0 2 8 2 9 3 1 3 2 3 3 3 5 3 6 3 8 3 9 4 1 4 3 441 6 0 0 0 0 0 0 0 0 0 0 0 0 0 0

Table 5 Capacity (vehicle/h) of minor-road for left turning traffic at T-junction where saturation flow for near-side lane is 2000 vehiclelh8Acceptable gap in major-road traffic = 5.4 seconds

f l o w i n s a t u r a t i o n f l o w f o r m i n o r - r o a d ( c a r / h )N / S l a n e( v e h i c l e / h ) 7 0 0 8 0 0 9 0 0 1 0 0 0 1 1 0 0 1 2 0 0 1 3 0 0 1 4 0 0 1 5 0 0 1 6 0 0 1 7 0 0 1 8 0 01 0 0 6 4 5 7 3 1 8 1 7 9 0 3 9 8 9 1 0 7 5 1 1 6 1 1 2 4 6 1 3 3 2 1 4 1 8 1 5 0 4 1 5 9 02 0 0 5 9 2 6 6 6 7 3 9 8 1 2 8 8 6 9 5 9 1 0 3 3 1 1 0 7 1 1 8 0 1 2 5 4 1 3 2 7 1 4 0 13 0 0 5 4 1 6 0 4 6 6 6 7 2 8 7 9 1 8 5 4 9 1 6 9 7 9 1 0 4 2 1 1 0 4 1 1 6 7 1 2 3 04 0 0 4 9 2 5 4 5 5 9 7 6 5 0 7 0 3 7 5 6 8 0 9 8 6 3 9 1 6 9 6 9 1 0 2 3 1 0 7 65 0 0 4 4 5 4 8 9 5 3 3 5 7 8 6 2 2 6 6 7 7 1 2 7 5 7 8 0 2 8 4 7 8 9 2 9 3 76 0 0 4 0 0 4 3 6 4 7 3 5 1 0 5 4 8 5 8 5 6 2 3 6 6 1 6 9 9 7 3 7 7 7 5 8 1 37 0 0 3 5 7 3 8 7 4 1 7 4 4 8 4 7 9 5 1 1 5 4 2 5 7 4 6 0 5 6 3 7 6 6 9 6 0 18 0 0 3 1 6 3 4 1 3 6 6 3 9 1 4 1 7 4 4 3 4 6 9 4 9 5 5 2 1 5 4 8 5 7 4 7 0 19 0 0 2 7 8 2 9 7 3 1 8 3 3 9 3 6 0 3 8 1 4 0 2 4 2 4 4 4 6 4 6 7 4 8 9 5 1 11 0 0 0 2 4 1 2 5 7 2 7 4 2 9 0 3 0 8 3 2 5 3 4 2 3 6 0 3 7 8 3 9 5 4 1 3 4 3 11 1 0 0 2 0 7 2 2 0 2 3 3 2 4 6 2 6 0 2 7 4 2 8 8 3 0 2 3 1 7 3 3 1 3 4 5 3 6 01 2 0 0 1 7 6 1 8 6 1 9 6 2 0 6 2 1 7 2 2 8 2 3 9 2 5 1 2 6 2 2 7 4 2 8 5 2 9 71 3 0 0 1 4 6 1 5 4 1 6 2 1 7 0 1 7 8 1 8 7 1 9 6 2 0 5 2 1 3 2 2 2 2 3 1 2 4 11 4 0 0 1 1 9 1 2 5 1 3 1 1 3 7 1 4 3 1 5 0 1 5 7 1 6 3 1 7 0 1 7 7 1 8 4 1 9 11 5 0 0 9 4 9 8 1 0 3 1 0 7 1 1 2 1 1 7 1 2 2 1 2 7 1 3 2 1 3 7 1 4 2 1 4 71 6 0 0 7 1 7 4 7 7 8 0 8 4 8 7 9 1 9 4 9 8 1 0 2 1 0 5 1 0 91 7 0 0 5 1 5 2 5 4 5 6 5 9 6 1 6 3 6 6 6 8 7 1 7 3 7 61 8 0 0 3 2 3 3 3 4 3 5 3 6 3 8 3 9 4 1 4 2 4 4 4 5 4 71 9 0 0 1 5 1 5 1 6 1 6 1 7 1 7 1 8 1 9 1 9 2 0 2 1 2 12 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

.!:. 13. Mean discharge rates from a car-park exit in terms or

~reservoir size and main-road now< ; (Gate service capacity 200 car/h)?u250.;C C a l c u l a t i o n :'"'w A m i n i m u m o f t h r e e e x i t b a r r i e r si s r e q u i r e d .. . T h e c o m b i n e d d e s i g n c a p a c i t y o f t h r e e b a r r i e r si s8 10

~ c a r s p e r h o u r . A 1 0% r e d u c t i o n i n b a r r i e rc a p a c i t y w i l le t h e r e f o r e b e a c c e p t a b l e g i v i n g a b a r r i e r o p e r a t i n gu c a p a c i t y of 2 4 0 c a r s p e r h o u r .C a s e A - e a c h b a r ri e ro p e r a t e s a t 2 4 0 c a r s p e r h o u r .T h e f l o w s i n t h e n e a r s i d e l a n e o f t h e r o a d o u t s i d e e a c h~ b a r r i e r a r e :~- b a r r i e r 1 5 0 0 v e h i c l e s p e r h o u rc 100 b a r r i e r 2 5 0 0 + 24 0 = 74 0 v e h i c l e sp e r h o u r~ 0 1200: : I : Main-road flow: nearside lane, vehicle/h b a r r i e r3 7 40 + 2 40 = 98 0 v e h i c l e sp e r h o u r

2 2


24/59

. . .';c. .s:'""es:; 150~I:o. .;:[1000~---:2~00::--~4:-:!0~0--::-!:-::---~::--~:-::---:'12:-:'00

"'ain-road flow: nearside lane, vehicie/h14. Mean discharge rates from a car-park exit in terms ofreservoir size and main-road flow(Gate service capacity 270 car/h)?

15. Mean discharge rates from a car-park exit in terms ofreservoir and main-road flow(Gate service capacity 400 car/h)"450r-----~----,_----._----~----_,----_.

Refer to Fig. 17 (for barrier with service capacity of270 cars per hour). Use 10% capacity reduction graph.By inspection:barrier 1 vehicle reservoir 1carbarrier 2 vehicle reservoir 2 carsbarrier 3 vehicle reservoir 6 carsItmay be more convenient to have vehicle reservoirsof the same size in which instance Case B applies.Case B -- vehicle reservoirs of the same size:Refer to Fig. 14 (for barrier with a service capacity of

270cars per hour). Check ifa 2car reservoir isadequate.barrier 1 flow on road 500 vehicles per hourbarrier capacity 265 cars per hourbarrier 2 flow on road 765 vehicles per hourbarrier capacity 245 cars per hour

s:C IIu:EC II>

'0oo. .,c5~Gate service ccpccit y 200 Garth

12Reservoir size, Gar spaces

16. Relationship between percentage reduction in systemcapacity, main-road flow and reservoir size for a gateservice capacity of 200 car/h9

17. Relationship between percentage reduction in systemcapacity, main-road flow and reservoir size for agateservice capacity of 270 car/h"1200r-~~~~~-'~::~:::::J::::::C:~~

s:Q; 0us:C II>~~

VI '0. . 0v e0Q. ,VI c'0~Gate service capacity 270car/h

2 6 B 10 124Reservoir size, car spaces

barrier 3 flow on road 1010 vehicles per hourbarrier capacity 210 cars per hourTotal barrier capacity = 265 + 245 + 210 = 720 carsper hour.The total exit flow from two barriers dischargingthrough the same T-junction may not approach twicethat of a single barrier in similar conditions owing tomutual interference between the two traffic streams.TurnoverTurnover is a measure of the use made of a car park andis the number of times a stall is used during a day. It iscalculated by dividing the number of cars entering thecar park during the day by the number of stalls in the car

23


25/59

1200.----,-----.-------r-----,---,------,Percentagereduction insystem capacity

3020105

o

Reservoir srze, car spaces18. Relationship between percentage reduction in systemcapacity. main-road Dow and reservoir size for a gateservice capacity of 400 carlh9

park. Thus a car park used solely by drivers parking allday, for instance while they are at work, would have aturnover of 1if it were fully occupied and less than 1ifi twere not. Turnovers of car parks vary significantly andturnovers up to over 12have been reported for shoppingcentre surface car parks.A high turnover is associated with a short stay and ahigh volume of internal movement. Attention is drawnto the recommended stall width of2.500m for short-stayparking in subsection 3.3. The additional width of stall

24

over the general width of2.400m facilities loading cars aswell as the parking and unparking of cars. The formulaein subsection 3.5 enable the effect of varying thedimensions of layouts and the parking angle to beevaluated. In addition, for a high-turnover car-park,short multiple-search paths are desirable, and it isdesirable to lay them out on a systematic basis tofacilitate a systematic search by drivers for a vacant stall.It is suggested that the split-level layout is unlikely toprove satisfactory for a high turnover owing to therelatively complicated search paths associated withcertain stalls. For a high turnover the flat-deck layout islikely to be preferable with clear-span construction togive drivers good visibility and to facilitate parking andunparking. Clearway ramps both up and down may berequired. Signing, both directional and of informatorynature, for vehicles and pedestrians is also required.It is recommended that a short-stay high-turnover carpark be planned in association with the development it isintended to serve. Pedestrian access should be direct andshort, and the lift capacity must be adequate to meet thedemand.In surface car-park design the requirement to cater fora short stay and high turnover usually involves areduction in the ratio of stall area to total car park area,that isin a reduction in the static efficiency of the layout.This method of providing for a high turnover is lessacceptable in multi-storey and underground car parksbecause of the cost involved. If then a multi-storey orunderground car park is being planned in associationwith surface car parking it is suggested that considera-tion be given to using surface car-park capacity for theshort-stay high-turnover traffic and the parking struc-ture for the longer stay lower-turnover traffic. Thus in atown centre that may be short-stay high-turnover de-mand for shopping and a longer-stay lower-turnover

demand for employee parking which it may be possibleto accommodate in the structure.

12


26/59

4 Vehicular and pedestrian control

4.1 Vehicle controlIntroductionFor the full dynamic capacity of a car park to be attained,traffic must flow smoothly into, out of and within thebuilding, so enabling the driver to enter and park andsubsequently relocate his car and leave as easily andquickly as possible.Smooth and rapid traffic flow can be achieved only bythe careful design of the car park and the intelligentselection of the parking control system. It is apparentthat the layout, location and function of each car parkwillinfluence the selection of the parking control systemto be adopted.Traffic control is enforced in car parks at variousstages:at entrywithin the car parkin the collection of parking feesat the exit.Entry controlWhenever controlled entry is required, either for charg-ing purposes or to prevent congestion in the car park, thechoice has to be made between rising-arm and rising-step barriers. These may be accompanied by trafficsignals CAR PARK FULL signs, ticket-issuing machines andSEASON TICKET ACCEPTANCE machines.

Lifting-arm barriersLifting-arm barriers are generally to be preferredsince they are easily visible to the motorist andstraightforward in operation. While the mechanismis robust, the arms are easily damaged and mayrequire frequent maintenance and repair arisingfrom accidental damage or vandalism.Rising-step barriersRising-step barriers consist of a steel plate that canbe mechanically raised from its 'down' position levelwith the roadway to its 'up' position in which itprotrudes above the road surface to form a barrier tomotor traffic. These barriers, which are more ex-pensive to purchase than barrier arms, have beenfound to be more resistant to vandalism and also toprovide a more positive vehicle barrier. Cases havebeen reported of vehicles being damaged either bymalfunction of the barrier or because they were notimmediately visible to motorists, and it is thereforerecommended that they should always be used inconjunction with a traffic signal that should showred when the barrier is up and green when it islowered.Because of their greater vandal resistance, theyhave been used for the control of unattended carparks with some success, often in conjunction withcollapsible traffic plates at the exit. These plates,

which are hinged at ground level on their leadingedge, are so arranged that free traffic flow ispermitted in one direction while providing a positivebarrier to vehicles travelling in the other.Capacity of entry lanesThe vehicle capacity of entrance lanes willdepend on themeans of fee collection adopted. In general terms themaximum capacities for each system are:

Capacity of a single lane, cars/h

no ticket issueautomatic ticket issuebarrier arm550450

rising step500450In designing car-park entry lanes it is important torecognize that the maximum efficiency will be achievedwhen motorists can drive into the car park in a straightline and that capacity will be reduced as bends to left orright are introduced. It is particularly important whentickets have to be obtained prior to the barrier arm toensure that the motorist can remove the ticket from theissuing machine with ease while seated in his car. Thiscan be particularly difficult to arrange with a left-handbend immediately prior to the entrance.Where access to a car park is by way of a ramp, theentry control should never be located on the ramp and,wherever possible, controls should be sited to avoidqueuing on the ramp itself.

Control within the car parkOnce a motorist has passed through the entrancecontrol, his aim will be to find a vacant stall asconveniently situated to his purpose as appears likely tobe available. In order to ensure the convenient andefficient operation of a car park it is, therefore, essentialto install a clear system of signs and floor markings. Incar parks housing up to 400 to 500 cars it is usuallysufficient to install signs and markings to indicate theroutes the motorist may follow and to leave to him theproblem of precise location of a vacant stall.In larger car parks this approach is too haphazard andusually results in delay and inefficient operation. As aresult it isusual to divide large car parks into units of 100to 300 stalls and to guide incoming cars to units withvacant stalls. This guidance can be achieved by usingelectronic detectors that activate vehicle counters thatconstantly monitor the occupancy of units. These coun-ters automatically switch internally illuminated signs toguide incoming motorists to units that have vacant stalls.While it is unusual to install such a guidance system incar parks of 500 stalls or less, there may be circumstancesin which it will be helpful to motorists to do so.While electronic control systems are often necessaryin large car parks, they should be avoided whenever it ispossible through the design of the car park. This can be

25


27/59

achieved by providing a logical search path that theincoming motorist will follow through the car park andwhich will enable him to find a parking space with ease.It is recognised that there will be instances where, inorder to take advantage of small or awkward shapedsites, it will be necessary to construct car parks that relyentirely for their successful operation on electroniccontrol equipment, and this may be justifiable incongested city sites. However, as has been noted above,a

Documents

Recommendations on Multi Storey Car Park Design