Highways in Residential and Commercial Estates · Highways in Residential and Commercial Estates...

D e s i g n G u i d e

P a r t Tw o

Highways in Residential and Commercial Estates

H i g h w a y s i n C o m m e r c i a l E s t a t e s

D E V O NC O U N T Y C O U N C I L

E N V I R O N M E N T

HI G H W A Y S I N CO M M E R C I A L ES T A T E S

PA G E 1 JA N 96

PART 2

HIGHWAYS INCOMMERCIAL ESTATES

CONTENTS

Section

1. Introduction

2. General Design Considerations

3. Detailed Characteristics of Commercial Roads

4. Technical Details

HI G H W A Y S I N RE S I D E N T I A L A N D CO M M E R C I A L ES T A T E S - DE S I G N GU I D E

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PA R T TW O - HI G H W A Y S I N CO M M E R C I A L ES T A T E S

PA G E 3

SECTION 1

INTRODUCTION

This Part of the Design Guide sets out the philosophies and detailedguidance on the layout of commercial estates. A commercial estate iswhere there may be one or more premises that are industrial, retail,business, warehouse or office in character. The Planning Frameworkwithin which proposals are considered and how adoption is achieved aredealt with in Part 3 of the Guide.

The general and detailed requirements are progressively discussed.Particular note should be taken of the advice on how narrower roads candiscourage on-street parking, providing sufficient on-site parkingfacilitates are available for each commercial premises.

Developers and their agents are specifically requested to note theadvantages in certain instances of a design brief as set out in Section 2.2.Early discussion on the production of a design brief will assist the rapidapproval of the estate layout.


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HI G H W A Y S I N CO M M E R C I A L ES T A T E S

PA G E 5

(a) to define a commercial estate road system that minimises theconflict between vehicles, pedestrians and cyclists

(b) to promote road layouts that encourage low vehicle speeds withinthe development

(c) to provide safe and convenient routes for pedestrians and cycliststhat integrate with existing or proposed routes outside thedevelopment site

(d) to assist in obtaining adequate and convenient off-street carparking facilities in order to reduce the dangers andinconvenience caused by on-street parking

(e) to provide on-street car parking facilities only where it is suitableand safe to do so, and in order to deter parking elsewhere

(f) to define adequate individual accesses and junctions on to theestate road, thus reducing the damage and maintenance to theestate streets and the dangers associated with excessivemanoeuvring of commercial vehicles in the estate road

(g) to encourage adequate on-site facilities for commercial vehicles,thus reducing the damage and maintenance of the estate streetsand the dangers and inconvenience of on-street parking

(h) to enable the public utilities and other statutory bodies to provideand maintain their apparatus and services with the minimuminconvenience to the users of the estate streets

(i) to suggest how commercial estate roads and footpaths can respectthe character of environmentally sensitive areas in terms ofappearance and use of materials, where such development isconsidered appropriate

(j) to ensure that the new development can be adequately served bypublic transport.

The Objectives

of the Guide

are

Thus, good commercial estate road and footpath design will promote asafe and efficient business environment. If excessive street damage is tobe avoided, adequate off-street and on-site vehicle facilities should beprovided, so that the roads are safe and functionally attractive.

SECTION 2

GENERAL DESIGN CONSIDERATIONS -ROADS AND FOOTPATHS

2.1 MAIN OBJECTIVES FOR LAYOUT

AND DESIGN

2.1.1 The aim of this Guide is to show how the design and construction ofcommercial estate roads and footpaths can be safe, convenient for theirusers and not costly to maintain. Good road and footpath design willproduce an efficient and functional layout, as well as an estate that is notunpleasing to the eye.

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2.2 THE DESIGN BRIEF

2.2.1 It would be very helpful if a Design Brief were drawn up for commercialdevelopments, especially for any development over 1.2 ha. This willenable the Local Planning Authority, the Highway Authority, thedeveloper and any other interested body to agree the requirements forthe development at an early stage so that it is well integrated into thesurrounding area both in vehicular, cycle and pedestrian links, and sothat the highway layout functions adequately. An agreed Design Brief,produced at an early stage, should speed up the approval of the finallayout.

2.2.2 The Design Brief would undoubtedly deal with matters related to the typeof development. It will be especially concerned with how the issues ofsustainability can be addressed in the design; in particular, theincorporation of other transport modes into the scheme, whether publictransport (bus or rail), cycling or walking.

2.2.3 It will probably also deal with the preferred layout for the roads andfootpaths, the type of materials to be used and the extent of anylandscaping schemes. It may also deal with any specific design problemsrelating to the incorporation of the development into the existing streetscene or its relationship with other sensitive areas.

2.2.4 The contents of the Brief would depend on the particular circumstancesof the development, but a check list for the highway aspects of a DesignBrief is given in Part 3 of this Design Guide, paragraph 1.3.8. Points toconsider including are:• the main points of access to the development for vehicles, pedestrians

and cyclists • any off-site highway improvements that may be required • any particular problems associated with the existing highway network

in the vicinity and any measures required within the site to ensure thatextraneous traffic is excluded as far as practical

• whether, in some cases, a Traffic Impact Analysis may be required toidentify the scheme’s effect upon the existing highway network

• whether, for larger developments, the Local Planning Authority mayrequire an Environmental Statement.


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Why a Design

Brief is

Recommended

What a Design

Brief May

Contain

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2.3 GENERAL DESIGN CONSIDERATIONS

2.3.1 This Guide specifies the characteristics of a road that is required to servea given size of development. The typical width of 6.0 metres for all butthe busiest of roads is intended to discourage on-street parking (exceptin dedicated parking bays). Culs de sac should be avoided, except wherethe development served by a particular road is small in size.

2.3.2 Because a commercial development will have to cater for large vehicles,traffic calming designed to fully restrain the speed of cars is seldompossible. Nonetheless, speed restraint can be achieved to a certain extentby following the principles contained in section 2.4.

2.3.3 However, some commercial estates, for instance office developments, willneed to cater for few large commercial vehicles. Where the typicalgeneration of a development is predominantly private cars, withcommercial vehicles providing only the occasional light delivery, it maybe more appropriate for the roads to be laid out (in width and trafficrestraint) in a similar manner to a residential estate. The principles ofthe guidance given in Part 1 “Highways in Residential Estates” are then tobe followed.

2.3.4 Commercial vehicles need a large amount of space to manoeuvre, evenwithin the carriageway. Therefore:-• culs de sac should be avoided as they would require large turning

heads• junctions require careful setting out in order to allow larger

commercial vehicles to drive through them on a natural line (seeSection 4)

• accesses need to be designed to accommodate all sizes of vehicle (seeSection 4); in order to reduce the impact of such wide accesses,shared accesses are recommended where the layout of adjacentpremises permits.

2.3.5 Although suggestions are given in this Guide as to what layouts aresatisfactory, it is up to the designers themselves to satisfy themselves andthe Highway Authority that the scheme proposed will function for alltypes of vehicle that may wish to use it. For instance, the designer mayneed to demonstrate to the Engineer that all anticipated vehicles canmanoeuvre on the road layout. Also, in some cases, it may be that aroundabout or other solution is necessary because of flow and geometryat some junctions within the estate.

2.3.6 Throughout the road system, adequate forward and junction visibilitymust be provided at all times. Section 4 gives full details of the requiredvisibility for the various elements in the hierarchy. Lower visibilitystandards will only be accepted in specific instances where it is clear thatvehicle speeds will be below the general design speed of the road.

2.3.7 Kerb heights are to be 150mm between accesses, in order to lessen theextent of highway damage caused by vehicle over-run. This will improvethe appearance of the estate and the safety of pedestrians.

Overall

Philosophy of

Design

Office

Development

Geometric

Standards

Visibility

Requirements

Kerb Heights

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2.3.8 Pedestrian crossings will normally be at traffic calming features and atjunctions.

2.3.9 Only highway drains and public sewers are permitted under carriageways,except where services connect to individual premises. How water isdisposed of from highway drains must be agreed with the HighwayAuthority prior to the completion of the Section 38 Agreement.

NO ESTATE ROAD SYSTEM WILL BE ADOPTED UNTIL THE PUBLICSEWERS ARE ADOPTED BY THE RELEVANT WATER COMPANY ANDTHE STATUTORY SERVICE COMPANIES HAVE STATED THATTHEIR INSTALLATIONS ARE TO THE REQUIRED STANDARD.

2.4 TRAFFIC CALMING

2.4.1 The design speed of commercial roads is 25mph or less. This can only beachieved by design, since control by legislation or signing is impracticaland is not necessarily effective. The highest level of traffic calming thatcan be achieved should be provided. If the development consists solely ofoffices, then traffic calming similar to that in residential developmentshould be considered (see paragraph 2.3.3). However, i f thedevelopment is mixed or consists of industrial or warehousing units, thenit is likely that little in the way of geometric or physical restraint can beprovided.

2.4.2 However, traffic calming can still be achieved by a mixture of thefollowing:-• junctions that cause traffic to stop or slow • ramps at the entrances to low speed shared surface areas • gateways • special treatment at junctions (see below).

(Note that reduced vehicle speeds are not achieved by reducing visibilitystandards. Lower visibility requirements are only possible if the designspeed of the road is reduced).

2.4.3 On Commercial Access Roads the spacing of traffic calming featuresshould be approximately 100 metres; suggested types of calming featureare given in Section 4. Unless the road is part of a loop road system, analternative route should be available when a calming device that narrowsthe road to one lane is subject to remedial works.

2.4.4 Vehicle/cycle/pedestrian conflict occurs mainly at junctions. As a trafficcalming measure, therefore, road junctions within a commercial estateare to be block paved with a rumble strip formed from natural orsimulated stone setts, as detailed in para. 4.2.4 (ii) and 4.5.2 (ii).


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Pedestrian

Crossings

Drainage and

Other Services

How Traffic

Calming

Functions

How Lower

Speeds Can Be

Achieved

Traffic Calming

Features -

Spacing and

Alternative

Routes

Junctions

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2.5 PRIVATE COMMERCIAL COURTYARDS

(SHARED SURFACE ROADS)

2.5.1 Private Commercial Courtyards are ‘shared surface roads’, which,although they will not be adopted by the Highway Authority, neverthelessare an integral part of the whole estate. These are roads where thetraditional format of a carriageway and segregated footway is replaced bya single highway surface that is used by pedestrians, cyclists and vehicles.Shared surfaces are particularly suitable to serve groups of smallcommercial units covering a total area of up to one acre; the central coreshould provide the access road and turning facility with each of thecommercial units gaining access from it. They thus provide theopportunity for low cost small units for cottage size industries or starterunits.

2.5.2 The design of shared surfaces must encourage caution in the driver tokeep traffic speeds low. Unwanted traffic and parking on the carriagewayshould be eliminated by good design.

2.5.3 Unless adequate parking for all vehicles is provided off the central coreand it remains available and unobstructed, (i.e. not used for outsidestorage), this type of private commercial road wil l not operatesuccessfully.

Where Shared

Surface Roads

are Suitable

Layout and

Design

Adequate

Parking

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2.6 PROVISION OF PARKING

2.6.1 Adequate parking should be provided for all vehicles likely to visit aproperty within its curtilage; this includes employees’, delivery andvisitors’ vehicles.

2.6.2 The roads within a commercial estate are for the passage of vehicles andare not provided or maintained for parking, the latter being outside theHighway Authority’s role. The use of off-street vehicle parking andturning areas for the storage of materials is likely to result in on-streetparking and the obstruction of the access roads; therefore, vehicleparking and turning facilities required for a particular commercial unitshould be available for parking and turning at all times. If insufficientvehicle parking facilities are provided for a commercial unit or some ofthe spaces allocated to particular personnel, parking spills out onto thehighway. Therefore full on-site parking facilities should be provided andmaintained for that purpose.

2.6.3 Nonetheless, there is likely to be some demand for on-street parking; thisis to be accommodated by the provision of parking laybys along bothsides of commercial roads. They should be kept to a minimum and notbe situated near to road junctions, private accesses and traffic calmingfeatures. A commuted sum to cover their future maintenance will bepayable to the Highway Authority.

2.6.4 Where a Planning Authority and a developer are able to devise apermanent scheme to prevent or avoid the likelihood of on-streetparking, then the on-street parking lay-bys may not be required. Forinstance, if adequate visitor parking is provided which is visible from theroad and the entrance to the site, and buildings are designed so thattheir visitor reception area is set well back, then on-street parking will beless likely to occur.


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Parking

Standards

Roads are not

Intended for

Parking

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Accessibility by

Cyclists and

Pedestrians

....... in Larger

Schemes

2.7 PROVISION FOR CYCLISTS AND PEDESTRIANS

2.7.1 A separate cycleway and/or footpath system should be considered inorder to comply with the recommendations of Planning Policy GuidanceNote 13 (PPG13), so that walking or cycling is seen as a real alternative todriving. These routes should penetrate the development andconveniently link with the surrounding areas (shops, residential areasetc), and may often be entirely separate from the carriageway network.

2.7.2 Furthermore, it may be necessary to provide a cycleway either parallel tothe footway, or combined with the footway. The degree of segregationwill depend on anticipated pedestrian and cycle flows.

2.7.3 The proposed footpath /cycleway network should be indicated onsubmitted drawings to show how the network works as an overall system,including its links with external destinations.

2.7.4 In smaller schemes, where the development area is less than 1.2 ha, thecyclist may well be adequately catered for on the carriageway itself.However, footpath/cycleway links with other areas should be providedwhere possible.

2.8 PUBLIC TRANSPORT

2.8.1 Public transport provides a real alternative to car-borne travel, anddiscussions should be held with the Engineer at an early stage to seewhether it is likely that bus services will use the estate roads. Whereappropriate, the provision of rail facilities should also be considered.

2.8.2 Factors to be considered are:• the type and frequency of bus service • the planning of routes in relation to the road hierarchy and existing

bus routes • the provision of turning areas and bus bays, or preferably a loop road

system • the siting of bus stops, including shelters • the size of the bus likely to be used • access to rail facilities where appropriate.

2.8.3 Bus stops should be safe and accessible, both on the local distributor thatleads to the estate and within the estate itself. The location of bus stopsrequires careful planning so that obstruction to accesses, junctionvisibility and footpaths does not occur.

....... in Smaller

Schemes

Factors to be

Considered

Bus Stops

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2.9 LANDSCAPING AND SURFACE TREATMENT

2.9.1 Although the problems and solutions will be different from those of ahousing estate, the overall aesthetic appearance of the commercial estateshould nonetheless be considered, and this is best achieved by the carefulchoice of construction materials and boundary treatment. Each siteforms it own environment, and Planning Authorities will undoubtedlypay particular attention to the landscaping adjacent to each site.

2.9.2 Soft verges are not acceptable at the carriageway edge. Previous attemptsto provide soft highway verges on commercial estates have proved to be amaintenance liability and have tended to detract from, rather thanenhance, the appearance of an estate. Other forms of landscaping,however, will be considered by the Engineer.

2.9.3 Every opportunity should be taken to provide landscaping. Thefollowing are locations where specific treatment could be considered:-


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Where

Landscaping

Could Be

Provided (i) the entrance to the estate, including the main entrance visibilitysplays and gateways

(ii) the perimeter of the site where it fronts an existing highway orother public development

(iii) areas adjacent to particular street features that could benefitfrom soft landscaping (including tree planting), e.g. informationboards and the associated lay-by, bus stops, pedestrian focalpoints, traffic calming features

(iv) retained existing features, including trees (v) statutory undertakers’ above ground apparatus, e.g. screening

electricity substations, gas governor houses etc.; (these normallyugly features should be sited away from any prominent view)

(vi) the boundary between the highway and individual commercialunits; walls using local materials are more aesthetically pleasingthan timber fences

(vii) the parts of any forward or junction visibility splay areas that arenot required as part of the footway and are adjacent to thecarriageway; these could be paved in concrete block paviours orsimilar where the area is significant

(viii) over-run areas at junctions and bends; these are to beconstructed as per the specification but surfaced in an approvedcontrasting hard material

(ix) street lighting columns and other street furniture; these shouldbe properly located and well designed; any street furnitureshould be placed at the rear of the footway

(x) junctions within the estate; a block paviour treatment with anatural or simulated stone sett rumble strip approach wouldidentify this obvious pedestrian crossing area and provide anenhancement to the street scene

(xi) parking lay-bys adjacent to the carriageway; these should beblock paved to provide a visual relief to the bituminouscarriageway and footways.

Landscaping is

Important

Soft Verges not

Acceptable

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PA G E 13

2.9.4 The treatment of visibil i ty splays needs particular attention inenvironmentally sensitive areas, e.g. in Conservation Areas and villages.The impact of such splays can be limited by the careful siting of theaccess point, the use of a minimum visibility splay consistent with roadsafety, and the reinstatement (or introduction) of hedgebanks, hedges,or stone or brick walls to match the surrounding area.

2.9.5 In certain locations, relief to the black top appearance of the estate roadsand footways can be achieved using rectangular concrete block paviours.These could form the pavement finish, identify pedestrian routes acrosscarriageways, be part of the road junction treatment, or part of a trafficcalming feature.

2.9.6 The character of development can also be greatly enhanced by theretention of existing trees, hedgerows, banks, fences and stone walls.Existing features should be retained wherever possible but must beincorporated into the design rather than retained in isolation.

2.9.7 Landscaping is to be designed to avoid high maintenance costs. Shrubs,including ground cover shrubs, may be preferable to close mown turf,and should be selected to withstand possible ill-treatment and todiscourage vandalism by their sturdiness.

2.9.8 The responsibility for maintenance of landscaping schemes should bediscussed and agreed with the Highway and Planning Authorities inadvance. Landscaping within the adoptable highway may well be subjectto a commuted sum; however, it may also be advantageous to includeplanting and landscaped areas within individual commercial sites wherethe owner or operators of the particular site can maintain and enhancetheir immediate working environment.

Visibility Splays

Hard

Landscaping

Retention of

Existing

Features

Design for

Maintenance

Maintenance

Responsibility

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PA G E 14

Need for a

Design Brief

2.10 COMMERCIAL DEVELOPMENTS IN

VILLAGES AND HISTORIC TOWNS

2.10.1 Devon’s historic towns and villages often have a particular character, andthe introduction of a new commercial development requires carefuldesign to ensure that it blends with that which already exists. In suchsensitive areas, new roads can often change the character of theenvironment dramatically because the highway standards sought todaywere not necessary in former times. The challenge is to achieve a designwhich is safe but does not damage the locality.

2.10.2 Thus, the design of developments in villages and historic towns needs tobe approached in a sensitive manner. Each site should be considered asa special case, which needs to be given careful thought. The issuesinvolved are• how to maintain the often tightly compact street scene• keeping the scale of accesses to a minimum• the careful choice of materials.

2.10.3 Instead of looking at the pages of this Design Guide as a menu fromwhich to choose a road layout appropriate to the size of development, thedesigner could return to basic principles. The following factors may helpto produce a design that fits comfortably in the local environment:• access requirements need to be examined from first principles; the

types or size of vehicles accessing the site may have to be consideredso that the layout is adequate

• vehicle speeds in the vicinity of the development may be reduced,thereby reducing visibility requirements at the entrance to thedevelopment, possibly by introducing speed restraint or trafficcalming measures on the existing road

• materials and finishes should be locally distinctive; the interface betweennew and existing development may be perceived as the most prominentaspect of the scheme, and even small changes can have a dramatic effecton improving the relationship between the two; block paviours for theroad surface and reconstituted stone kerbs may be a requirement

• where pedestrian traffic flows in village developments are low then thefootway may be reduced in width to 1.25m with a grass or groundcover verge at its rear to make up the remainder of the normalfootway/service margin width

• street lighting design should be sympathetic to the setting of thelocality

• special arrangements for services should be considered to avoidexcessive standards

2.10.4 Where development is contemplated in sensitive locations earlydiscussion is recommended with both the local Planning Authority andthe Highway Authority in order to agree the design standards to beadopted.

Special

Considerations

The Issues

Basic Principles

of Design

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PA G E 15


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SECTION 3

THE DETAILED CHARACTERISTICSOF COMMERCIAL ROADS

3.1 THE ROAD NETWORK

3.1.1 The roads in a proposed scheme should be appropriate to their function,as described in the table below, for which further details are given in theSections following.

The roads that distribute traffic outside the commercial estates and arenot included in this Guide are:

Principal DistributorsDistrict DistributorsLocal Distributors

Within a commercial area, the types of road are as follows:-

A typical layout is illustrated on the opposite page:-

The Road

Network

Road Type Description Area ofDevelopment

Served

Type C1Commercial Roads that distribute traffic over 12 haDistributor within large estates.Roads

Roads that collect traffic within estatesType C2 and should be loop roads within the Commercial estate. up to 12 haAccess Roads The road may be a cul de sac where less

than 1.2 ha of development is served.

Type C3 Roads that collect traffic withinNarrow Commercial estates and provide an alternativeAccess Roads route within an estate road system.

Type CP41 Non-adopted Access up to 3Private Ways similar in form to commercialCommercial Access Type C2 culs de sac. units

Type CP42 A special type of access road thatPrivate Commercial serves a group of small commercial units up to 0.4 ha.Courtyards without a separate footway system.

The network also includes cycleways and footpaths from which motor vehicles are excluded.


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Local Distributor Road

Access Road C2

Access RoadC2

Private AccessWay CP41

Access RoadC2

Commercial Distributor C1

Access Road C2

Loca

l Dis

tribu

tor

PrivateCourtyardCP42

Cycleway/Footpath

Cycleway/Footpath

Cycleway/Footpath

Cycleway/Footpath

Link to ResidentialArea

Private Access Way CP41 Access Road C2

AccessRoadC2

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3.2 TYPE C1 COMMERCIAL

DISTRIBUTOR ROADS

3.2.1 Commercial Distributor Roads are through routes or transition roadswhich which serve large estates (generally over 12 hectares/30 acres) andwhich may be expected to carry over 150 commercial vehicles per day.Junction layouts may require special attention where traffic flows areheavy; junction capacity calculations may be required.

3.2.2 Direct access to individual sites is not permitted. The design shoulddiscourage vehicles stopping on the carriageway. Nonetheless, bus andinformation board laybys should be provided.


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Function

Accesses,

Laybys and

Parking

Detailed

Characteristics

of These Roads

Are

Design Speed 48 kph (30 mph) normally they will be subject toa speed limit of 30 mph.

Carriageway Width 7.3m widened on bends as necessary (see para. 4.3.7).

Junctions with District or Local Distributors:to comply with current DoT Technical AdviceNotes.

Centre Line Radii 60m between 60m and 75m, carriageway widening willbe required.

Kerbs 150mm upstand using 300 x 150 kerbs atcarriageway edge 6mm upstand at pedestrian crossing points.

Cycleways and The Commercial Distributor Road is to haveFootways footways on both sides, and a cycleway on at least

one side of the road segregated from othervehicular traffic (for details see Section 3.8). Where there is only a footway (i.e. the cycleway ison the other side of the road), it is to be 2.5m wide. Grass verges alongside commercial estate roadsare not appropriate.

Visibility splays Junction and forward visibility splays in excess ofthe footway requirement are to be surfaced inrectangular concrete block paviours.

Laybys The dimensions of laybys adjacent to informationboards are detailed in para. 4.4.3, and finished inconcrete block paviours.

Services Statutory Undertakers’ mains, cables and ductsare not permitted in the carriageway and shouldbe located in the footway/services’ margins withthe minimum of carriageway crossings. However,all sewers and highway drains should be located inthe carriageway.


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3.3 TYPE C2 COMMERCIAL ACCESS ROADS

3.3.1 Commercial Access Roads distribute traffic within smaller estates orconnect with Commercial Distributor Roads in larger estates (generallyserving between 6 and 12 hectares or 15 and 30 acres), and may beexpected to carry between 75 and 150 commercial vehicles per day. ACommercial Access Road network can serve up to 24 hectares (60 acres) if • it is in the form of a loop road off the end of a Commercial

Distributor Road, or • if it has two junctions with a Commercial Distributor Road, or • if its two equal or near equal halves are connected by a Narrow

Commercial Access Way.It can only be a cul de sac if less than 1.2 ha of development is served.

3.3.2 The layout given below and in Section 4 may generally be all that isnecessary, but in some cases it may be that a roundabout or othersolution is necessary because of traffic flow patterns or geometry.

3.3.3 Direct access to premises will be permitted whenever adequate off-streetparking and service vehicle facilities are provided. Shared accesses arerecommended to keep their number to a minimum. Turning facilities forcommercial vehicles must be provided within the site so that all vehiclescan enter and leave the public highway in forward gear.

3.3.4 Bus lay-bys should be provided where appropriate, and so shouldinformation board lay-bys on larger estates without CommercialDistributor Roads.

3.3.5 Where there is likely to be some demand for on-street parking, this is tobe accommodated by the provision of parking lay-bys along both sides ofthe road (see paragraph 2.6.3).

Function

Junctions with

Other Roads

Access

Laybys

Parking Bays

3.3.6 If the road extends into a Private Commercial Courtyard or Access Way,full-size commercial vehicle turning facilities must be provided at thelimit of the Commercial Access Road so that traffic does not have to usethe private roads as a turning facility. Junctions can serve as turningheads for the purpose of this requirement. A straight extension of anAccess Road into a Private Commercial Courtyard or Access Way is notpermitted.


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Detailed

Characteristics

of These Roads

Are

Design Speed 40kph (25mph)

Spacing of The maximum distance between speed restraintsSpeed Restraints is to be 100m (see para. 4.5.1); the road should be

part of a loop system, in order to allow analternative route when a particular traffic calmingfeature is subject to remedial works.

Carriageway Width 6.0m widened on bends as necessary (see para 4.3.7).

Radii of junctions Compound curves as shown in para 4.2.4 (ii) arerequired between types C1 and C2, and betweenC2 and C2 roads. (See also para 3.3.2).

Centre Line Radii 60m between 60m and 75m, carriageway widening willbe required.

Kerbs 150mm upstand using 300 x 150 kerbs atcarriageway edge 12mm upstand at vehicle entrances 6mm upstand at pedestrian crossing points

Cycleways and The Commercial Access Road is to have footwaysFootways on both sides, and a cycleway on at least one side

of the road segregated from other vehiculartraffic (for details see Section 3.8). Where there is only a footway (i.e. the cycleway is on the other side of the road), it is to be 2.5m wide. Grass verges alongside commercial estate roadsare not appropriate.


Laybys The dimensions of Bus, Information and ParkingLaybys are detailed in Section 4.4, and are to befinished in concrete block paviours.


Turning Heads

and Extensions

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PA G E 21

3.4 TYPE C3 NARROW COMMERCIAL ACCESS WAYS

3.4.1 A Narrow Commercial Access Way is a short single track road linking two‘halves’ of a Type C2 Commercial Access Road. It is not to be a cul de sac.

3.4.2 Direct access to commercial premises, either pedestrian or vehicular, willnot be permitted, due to the restricted width of the road. The planningpermission for an estate containing a Narrow Collector Road should bemade subject to conditions that do not permit the creation of pedestrianor vehicular access on to these roads.

3.4.3 The creation of a Narrow Commercial Access Way off a Local DistributorRoad or an existing classified road whose function is that of a DistributorRoad will not be permitted.

3.4.4 The junction between a Narrow Commercial Access Way and aCommercial Access Road or Way is to be in accordance with the layoutsdetailed in para. 4.2.4 (iii).

3.4.5 Narrow Commercial Access Ways can occasionally be blocked by vehiclebreakdown or road maintenance etc. Therefore, there must be analternative route over public highway that is available, especially foremergency vehicles.

Function

Accesses

Junctions

Detailed

Characteristics

of These Roads

Are

Alternative

Emergency

Route

Design Speed 32kph (20mph).

Carriageway Width 4.0m, or 3.0m if there is a separate cycleway, withlocal widening at bends.

Radii of junctions 15m at all junctions.

Centre Line Radii 60m.

Kerbs 150mm upstand using 300 x 150 kerbs atcarriageway edge.

Cycleways and The Narrow Commercial Access Way is to have aFootways cycleway on at least one side of the road

segregated from other vehicular traffic (fordetails see Section 3.8). Where there is only a footway (i.e. the cycleway ison the other side of the road), it is to be 2.5m wide. Grass verges alongside commercial estate roadsare not appropriate.



3.5 TYPE CP41 PRIVATE COMMERCIAL ACCESS WAY

3.5.1 A Private Commercial Access Way may serve up to three commercial unitsproviding each has adequate off-street vehicle parking and turningfacilities. Careful design is required to ensure that the pedestrian andvehicle access arrangements are adequate and safe and that asubstandard arrangement has not been devised to reduce the length ofadoptable street.

3.5.2 Shared off -street vehicle parking and turning facil i t ies for thecommercial units served by the shared access road may be acceptable.

3.5.3 Private Commercial Access Ways may be directly accessed from Type C2Commercial Access Roads.


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Function

Accesses

Detailed

Characteristics

of These Roads

Are


Entrance/Surfacing The surfacing material is to differ from adjacentMaterial carriageways in order to indicate to the driver that

a different environment is being entered; a dropped kerb with 6mm upstand is to be provided on the channel line of the main carriageway and demarcation provided where the adopted entrance changes to a private access way.

Carriageway Width 6.0m minimum with local widening at bends.

Radii of junctions 15m at all junctions

Turning Facilities On-site vehicle turning facilities will need toaccommodate the largest commercial vehicle.

Kerbs 150mm upstand using 300 x 150 kerbs at carriageway edge 12mm upstand at vehicleentrances 6mm upstand at pedestrian crossing points.

Footway/Service The footway/service margins shall be a 2.5m wideMargin footway on one side and a minimum 1m wide

paved clearance/service margin on the other sideif this is adequate for services and pedestrians.

Vehicle Parking On-site car and commercial vehicle parking andcommercial vehicle loading and unloading facilities for all vehicles likely to attend the site(s) should be provided. Its design should be suchthat all vehicles can be parked within the site,with no necessity to reverse from or on to a public highway.

Surface Water Adequate provision is to be made for the disposal Disposal of surface water from the access road, via a piped

drainage system with an approved outfall, which is not to be an adoptable highway drain.


PA G E 23 JA N 96

Private Commercial Access Roads will NOT be adopted by the HighwayAuthority and the Developer will be required to enter into a LegalAgreement to provide for future maintenance, either as landlord or asthe originator of a properly constituted Management Company whichconsists of all Owners, Tenants and Occupiers of properties using theAccess Road if liability to Advance Payment Code deposits are to beavoided.

Type CP41 Private Commercial Access Way

Mixed Office/Warehouse

HGV loading

Turningfacility

HGV loading HGVparking

Turning facility

Office development

Gateway

Pri

va

te A

cc

es

s W

ay

Line of kerbs, blocks, setts etc. to define limit of adoption

3.6 TYPE CP42 PRIVATE COMMERCIAL

COURTYARDS

3.6.1 A Private Commercial Courtyard is a cul de sac for the joint use ofpedestrians and vehicles. It provides direct access to small/startercommercial unit forecourts. The Commercial Courtyard may serve up toan overall area of 0.4 hectares (1 acre) of commercial development(including the buildings, forecourt, vehicle facilities and courtyard). Thesize of the individual commercial unit can be up to 150m.

3.6.2 The Courtyard will take the form of an access road that terminates in afull-size commercial vehicle turning facility and may well be constructedin block paviours laid to herringbone pattern. Demarcation is to beprovided where the adopted entrance changes to a private courtyard.

3.6.3 The forecourt of each unit will be accessed from the courtyard, which willprovide delivery vehicle access and parking for the particular unit. Thetotal parking requirement for a particular unit does not need to beprovided in the individual forecourt; 50% of the parking requirementcould be available in communal parking areas that also serve theneighbouring units, providing the parking area is directly accessed fromthe same courtyard.

3.6.4 A communal lorry parking area for a complex of small/starter units withaccess from the courtyard should be provided. One lorry space for every3 individual units is recommended.

3.6.5 A Private Commercial Courtyard will be permitted off a local distributorroad or lesser road if the entrance is laid out as detailed in figure 4.2.4(iv), which specifies a footway separate from the carriageway in thevicinity of the major road.

Type CP42 Private Commercial Courtyard


PA G E 24JA N 96

Function

Layout and

Construction

Parking

Access

Turning facility

Gateway

Pri

va

te R

oa

d

Line of kerbs, blocks, setts etc. to define limit of adoption


PA G E 25 JA N 96

Detailed

Characteristics

of These Roads

Are


Entrance/ The surfacing material is to differ from adjacent Surfacing carriageways in order to indicate to the driver that aMaterial different environment is being entered; a dropped kerb

with 6mm upstand is to be provided on the channel lineof the main carriageway and demarcation provided where the adopted entrance changes to a private access way.

Carriageway The carriageway width shall be 6.0m widened on bends Width in accordance with para. 4.3.7. The width may be reduced

to 5.5m if turning is possible within the forecourt area.

Radii of Minimum 10m, junctions and 15m with a Local Distributor Road.

Kerbs 40mm upstand at the edge of the carriageway 12mm upstand at accesses, and6mm upstand at pedestrian crossing points.

Footways Not required.

Highway The statutory undertakers’ mains and apparatus should clearance not be accommodated in the spine road but alongside strips/service the courtyard carriageway in paved margins. The margins margins should be of minimum 2m width, but where no services

are likely to be required it can be reduced to 1m wide.

Turning A full size vehicle turning head is required at the end of heads the courtyard, as detailed in figure 4.3.8. The turning

head within a Private Commercial Courtyard needs to only accommodate an 11m rigid vehicle if there is a full size commercial vehicle turning head at the courtyard entrance.

Vehicle On-site car and commercial vehicle parking, and Parking commercial vehicle loading and unloading facilities for

all vehicles likely to attend the site(s)should be provided; its design should be such that all vehicles can be parked within the site, with no necessity to reverse from or on to a public highway.

Surface Adequate provision is to be made for the disposal of Water surface water from the access road, via a piped drainage Disposal system with an approved outfall, which is not to be an

adoptable highway drain.

3.6.6 Private Commercial Courtyards will NOT be adopted by the HighwayAuthority and the Developer will be required to enter into a LegalAgreement to provide for future maintenance, either as landlord or as theoriginator of a properly constituted Management Company which consistsof all Owners, Tenants and Occupiers of properties using the Courtyard ifliability to Advance Payment Code deposits are to be avoided.

JA N 96

3.7 CYCLEWAYS WITH FOOTPATHS

3.7.1 This section deals with cycleways that are not alongside a carriageway.(See Section 3.8 where a combined cycleway/footway lies alongside acarriageway). Cycleways are routes for cyclists that motorised vehicles arenot permitted to use (with the exception of emergency and maintenancevehicles). Pedestrians, however, do have the right to use them. They maybe adjacent to footpaths, or the route may be unsegregated (i.e. sharedbetween cyclist and pedestrian with no separation by kerb or white line)where flows are expected to be low, but each situation must beconsidered on its own merits.

3.7.2 Unsegregated paths should generally only be provided where pedestriansregularly need to cross over them. The width of unsegregated pathsshould normally be 2.5m, but under certain circumstances localnarrowing to 2.0m may be allowed.

3.7.3 Segregated footpaths and cycleways should be distinguished from eachother by surface colour, texture, central white line or even upstand kerbin more heavily used sections. The surface treatment will be determinedby consultation with the Engineer, who will have regard to the type ofsurface treatment used on other cycle routes in the neighbourhood whengiving their approval. The width of each section (i.e. both cycleway andfootpath) shall be 1.5 metres if bounded by a verge, or 1.75m if boundedby fence, wall or the like.

3.7.4 Minimum forward visibility shall be 20m, increased to 30m where thedownhill gradient exceeds 5%.

3.7.5 Junctions with vehicular carriageways are to be laid out as in section4.2.4. Care should be exercised in the design of such layouts, bearing inmind the principle that the cycle track is a carriageway. Thus, proximityto other junctions, junction visibility and junction detailing (Give Waylines etc) need careful thought. The visibility requirements at priorityjunctions are as set out in paragraph 4.2.1, using the appropriate “y”distances and an “x” distance of 1.5 metres.

3.7.6 Where a cycleway crosses a footpath, the cyclist has precedence, and theappropriate “x” and “y” visibility distances for the pedestrian are 1.0mand 20m respectively.

3.7.7 The minimum headroom provided over cycleways should be 2.75 metres.

3.7.8 Provision should be made for the drainage of cycleways. Where adjoiningland is to be adopted as public open space by the Local Authority, it maynot be necessary to provide positive drainage, but this will depend onwhether the cycleway is on an embankment, side slope or cutting.

3.7.9 Cycleways should be pleasant to use in all cases, with no recesses thatwould cause concern for personal safety. Adequate lighting shall beprovided.


PA G E 26

Function

Unsegregated

Cycle Paths

Segregated

Cycle Paths

Visibility

Junctions

Headroom

Drainage

Security


PA G E 27 JA N 96

3.8 CYCLEWAYS WITH FOOTWAYS

3.8.1 Generally, cycleways that are combined with footways (i.e. alongsidecarriageways) will be unsegregated, except where very high pedestrian orcycle flows are expected. They are to be 2.5m wide, with a 0.5m wide hardverge between the path and the carriageway.

3.8.2 If segregated, the footway is to be 1.75 metres wide and the cycleway 1.5metres wide, with a 0.5m hard verge between the carriageway andcycleway

3.8.3 Careful design will be needed at points where the cycleway crosses thecarriageway, and consultation with the Engineer will prove helpful.Normally, “give way” markings will be necessary.

3.9 FOOTPATHS

3.9.1 Footpaths are defined as pedestrian routes located away fromcarriageways.

3.9.2 Footpaths to locations outside to the commercial development shouldfollow pedestrian desire lines, by linking features that generate or attractpedestrian traffic e.g. shops, residential areas etc. Where the footpathcrosses major roads the crossing points must be safe and convenient. Ifphysical segregation is not provided, barriers and other safety measuresmay be required. (Further guidance for the provision of crossing facilitiesfor the blind are given in Part 1 of this Guide and Department of theEnvironment Disability Unit Circular 1/91).

3.9.3 All footpaths should be direct and should be wide enough to suit theexpected level of use. A minimum width of 2.5m is normally required,but wider paths may be required where the full range of services islocated beneath. Their widths may vary in the following circumstances:• where less than the full range of services has to be accommodated and

pedestrian traffic is very low, widths may be reduced to a minimum of1.35m provided that frequent 2.5m wide passing places are provided,particularly where lamp columns and signs are located

• where access by emergency services or statutory undertakers’ vehiclesis required footpaths need to be strengthened and widened to aminimum unobstructed width of 2.75m

• where a footpath is to be used by both pedestrians and cyclists seesection 3.8 above

• where footpaths pass between fences, walls and buildings, the widthmay need to be increased to accommodate the likely level ofpedestrian traffic, and to give the feeling of personal security.

Function

Width

3.9.4 The minimum headroom provided over footpaths should be 2.4 metres.

3.9.5 Footpaths should be easy to use throughout the network for those withprams and wheelchairs. Steps should be avoided wherever possible but, ifunavoidable, the provision of suitable ramps or alternative routes to caterfor prams and wheelchairs may well be necessary.

3.9.6 To give a feeling of greater security footpaths should be open, with nohidden corners, well lit after dark and should be overlooked. Thepedestrian should be able to see from end to end.

3.9.7 Provision should be made for the drainage of footpaths. However, whereadjoining land is to be adopted as public open space by the LocalAuthority, it may not be necessary to provide positive drainage, but thiswill depend on whether the footpath is on an embankment, side slope orcutting.


PA G E 28JA N 96

Headroom

Ease of Use

Security

Drainage

BLANK


PA G E 29 JA N 96

SECTION 4

TECHNICAL DETAILS

4.1 INTRODUCTION

4.1.1 The dimensions and details given in this section are diagrammatic, andare the minimum requirements. The Highway Authority will be willing toconsider adopting layouts that are slightly in excess of what is shown, if itresults in a more interesting layout.

4.1.2 Many of the requirements of commercial estate roads are given in Table4.1.2 following this page. These are expanded in the followingparagraphs, tables and diagrams.

4.2 JUNCTIONS AND ACCESSES

4.2.1 The provision of adequate visibility at junctions is vital for the safety of allroad users. The table below gives the basic dimensions required for thedifferent road types.

Table 4.2.1 Visibility Splays


PA G E 30JA N 96

Adequate

Visibility

Major Road Type

Distributor Roads Roads WithinOutside Commercial Estate Commercial Estates

C1 C2 C31 C32

Major Road........Design Speed kph 100 85 70 60 48 32 24 24

mph 62 53 44 37 30 20 15 15

....Speed Limit (mph) 60 50 40 30 30 30 30 30

X Distance (m)(1) 9.0 9.0 9.0 9.0 4.5 4.5 4.5 4.5

Y Distance (m) 215 160 120 90 60 45 33 23

Source: TD42/95 and DB32

Notes

(1) The X distance may be reduced from 9.0m to 4.5m, and from 4.5 to 2.4m for a private access, at thediscretion of the Engineer.


JA N 96

THE DETAILED CHARACTERISTICS OF COMMERCIAL ROADSTABLE 4.1.2

Definition Access from/to Direct access Design Other Carriageway Junction Centre line Spacing of Kerbs Cycleways Footways Services Parkingother road types to premises Speed (kph) Requirements Width Radius radius Speed

at vehicle pedestrianwith more Restraints carriagewayaccess crossing pointsmajor road

Serves as a Required both sides, In footway No on-streetCommercial Through route on through route or Not permitted Stopping discouraged. See current At least minimum width 2.5m parking

C1 Distributor large estates transition road from to individual 48 Bus and Information 7.3m DoT60m

150mm 6mm on one (may be shared with permittedRoad >12ha/30acres Classified Road to sites laybys to be provided standards

minimumside cycleway on

collector roads one side)

Collects traffic from Permitted when Information board type C3, CP41 & development laybys to be provided Required both sides,

Commercial CP42 roads has adequate where no C1 Road. Compound At least minimum width 2.5m On street parkingC2 Access Normal maximum Yes off-street 40 Full-size turning 6.0m curve,

60m100m 150mm 12mm 6mm on one (may be shared In footway permitted

Road area served parking; facilities required see para 4.2.4minimum

side with cycleway in bays12ha/30acres shared accesses where effectively on one side)

(if loop see para 3.3.1.) recommended cul-de-sac

4mNarrow Link Not Direct access not There must be (or 3m if 60m At least Min width 2.5m

C3 Commercial between two permitted permitted to 32 an alternative there is 15m minimum 150mm 6mm on one (3m if shared In footway No parkingAccess Way C2 roads off C1 individual sites route a separate side with cycleway)

cycleway)

Private road accessing Surfacing material 2.5m footway onPrivate up to 3 units. Permitted to differ from main at least one side, In footway Adequate

CP41 Commercial Must be adequate off C2 Permitted 24 carriageway. 6.0m 15m 150mm 12mm 6mm 1m margin or off-street parkingAccess Way vehicle and Turning head where margin to be provided

pedestrian access required no footway

Permitted Surfacing material 10m Both dedicated and Private Private Courtyard off Local to differ from main or 15m at In communal parking

CP42 Commercial accessing small/ Distributor Roads Permitted 24 carriageway. 6.0m junction with 40mm 12mm 6mm Not Required paved to be provided, Courtyard starter units and Commercial Turning head Local margin accessed from

Access Roads required Distributor courtyard


JA N 96

THE DETAILED CHARACTERISTICS OFCOMMERCIAL ROADSTABLE 4.1.2


PA G E 31 JA N 96

Figure 4.2.1 Visibility Splays

Access driveor road

Y Y

X

See para 4.2.2

Channel of major road

4.2.2 Visibility Splays should be clear of any obstructions that are higher than300mm above the channel level over the hatched area of the figureabove. This will then allow any planting to grow a further 300mm, but inany case the overall height should never exceed 600mm at any time ofyear. Vertical obstructions to visibility such as lamp columns and trees willbe accepted provided that in combination they do not create a solidvisual barrier.

Clearance of

Obstructions

Minimum

Spacing

between

JunctionOn Distributor On Access

Roads Roads

Junctions on same side of road 90m 90m

Junctions on opposite side of road 45m 45m

Private Access from junctions - 30m

[Measurements are centre-line to centre-line]

4.2.3 The minimum spacing between junctions should be as follows:

Table 4.2.3 Minimum Spacing of Junctions

Junction Layout

-Entry to an

Estate

4.2.4 (i)The junction at the entrance to a commercial estate shall be inaccordance with current technical advice, taking into account thefunction of the main road in the highway network, the traffic flows on themain road and those from and into the commercial estate.

4.2.4(ii)Within an estate junctions will be laid out as follows. (However, in somecases it may be that a roundabout or other solution is necessary becauseof traffic flow patterns or geometry).

Figure 4.2.4(ii) Junction Layout


PA G E 32JA N 96

Junction Layout

-Within an

Estate

4.2.4(ii) junction layout

Visibility splay

2.5m wide footway

2.5m wide cycleway/footway +0.5m hard verge

Bituminous or DBM surfacing

Block paving

2m wide stone sett rumble strip(the position of these rumble strips dependsupon the position of pedestrian crossing pointsand any central refuges)

150 mm kerb upstand throughout(except at pedestrian crossing points)

Compound radius (see detail) 8

1

2

1

3

5 3

2

2

2

3

2

4

4

4

6

6

6

2

3

4

5

6

7

8

7

MAJOR MINORCommercial CommercialAccess Road Access Road


PA G E 33 JA N 96

When larger vehicles attempt to enter a side road, some considerablelength is needed for them to regain their own side of the road.Therefore, to assist larger vehicles to follow as natural a line as possiblebetween two Commercial Access Roads or between a CommercialDistributor Road and a Commercial Access Road, the geometry of thekerb line shall be as follows:-

Junction

Geometry

34m R20°

20°

20°

20°

12m R

12m R

11.69m 9.22m

11.69m

9.22m2.05m

2.05m

34m R

15m

3.0m 2.5m footway

(or 3.0m including 0.5m hard vergeif cycleway incorporated)

Road widened tosame width as

major road overinitial 30m

Figure 4.2.4(iii) Junction Layout

Figure 4.2.4(ii) (b) Junction Geometry

MAJOR MINORCommercial Narrow CommercialAccess Road Access Way

A gateway feature should be incorporated, as illustrated in sections 3.5 and 3.6.


PA G E 34JA N 96

15m

Change ofsurfacing material

Line of kerbs, blocks or setts etc. to define limit of adoption

granite settsor similar presence of footways depends

upon category of road

3m radius

3m radius

preformedcycle logoto diag.1057

Shared Cycle/PedestrianRoute

cycle lanewidenedfrom 1.5m to 2.5m overlast 6m

Segregated Cycle/PedestrianRoute

2.5m

1.5m 1.5m

carriageway

MAJOR MINORCommercial Private CommercialAccess Road Access Way or

Courtyard

Cycleway Junctions

Figure 4.2.4(iv) Junction Layout

Figure 4.2.4(v) Junction Layout


PA G E 35 JA N 96

4.2.5 Individual (or shared) accesses must accommodate the largest vehiclelikely to use them, which is unlikely to be less than an articulated or rigidlorry. Dimensions that accommodate such vehicles are shown below;however, each case should be considered on its own merits as angle ofapproach or the frequency of larger vehicles etc. may dictate otherarrangements. The construction details shown below will distinguish anaccess from the adjacent footway.

Private Accesses

General

Demarcation strip between highway and private land

Contrasting material to footway

Dropped kerbs with 12mm upstand

Flush 150x125 kerbs (or similar)

Kerbs with 150mm upstand

Fall of crossover to be varied across its widthsuch that only a 1 in 40 fall exists over a one metrestrip at its rear

Footway

Minimum 9.0m wide if footway 2.5m wide 8.5m wide if footway 3.0m wide

30°

5

1

2

3

4

5

6

2

3

44

6

1

4.3 CARRIAGEWAYS

4.3.1 Widths, lengths between traffic calming features, and minimumhorizontal radii are given in Table 4.1.2.

4.3.2 The forward visibility required is the stopping distance needed byvehicles travelling along a road at the defined speed.

Table 4.3.2 Forward Visibility

Forward

Visibility

Speed - kph 48 40 32 24 16 8- mph 30 25 20 15 10 5

Stopping Distance (m) 60 45 33 23 14 6

Figure 4.2.5 Private Accesses

4.3.3 Forward Visibility on bends is to be provided as follows:

Figure 4.3.3


PA G E 36JA N 96

Forward

Visibility on

Bends

Calculation of

Forward

Visibility

“Envelope”

stopping distance

2345678234

5

6

7

8

A1

B2

3

4

5

6

7

8

1

1

stoppingdistance

1.5m

1.5m

2

Shaded area to be kept clear ofobstruction (see below)

4.3.4 At least the minimum visibility defined in Table 4.3.2 above should alwaysbe available to the driver at the design speed of the road. The envelopeof the area to be kept free of obstruction can be derived in the followingmanner:1. draw a line parallel to the inside kerb, 1.5m into the carriageway, to

represent the path of an approaching vehicle 2. obtain the design speed for the type of road from Table 4.1.2. The

required stopping distance for this design speed is given in 4.3.2above

3. measure the full stopping distance back from tangent point “A” aboveand divide the vehicle path into equal increments (say 3m), andnumbered

4. continue these increments sequentially around the curve until a fullstopping distance beyond tangent point “B” above is achieved

5. draw lines to connect increment points that are the stopping distanceapart; the resultant envelope is that which should be kept clear ofobstructions so that an object 0.25m high in the carriageway can beseen from the driver’s height of 1.05m.


PA G E 37 JA N 96

4.3.5 Gradients and Crossfalls shall be in accordance with the following table:

Table 4.3.5 Gradients and Crossfalls

Gradients and

Crossfalls

4.3.6 Vertical curves shall be provided in all instances where the algebraicdifference between adjoining straight gradients is in excess of 1%.

4.3.7 Widening is required on bends when the sum of the swept paths ofpassing vehicles is greater than the width of the carriageway. It is betterto alter the inner radius of the bend when accommodating this widening.

The following table gives the required width of carriageway for bends ofvarying radii subject to the minimum widths and radii specified for eachparticular road type:-

Vertical Curves

Widening on

Bends

Table 4.3.7 Widening of Carriageway on Bends

Inner Kerb Radius 30 40 50 60 70 80 90 100 110 120 130 140 150(metres)

Road to be widened to.....for 6.0m wide roads. 9.6 9.3 8.8 8.5 8.2 7.9 7.7 7.3 7.0 6.7 6.5 6.3 6.1

(metres)

...for 7.3m wide roads 9.6 9.3 8.8 8.5 8.2 8.0 7.9 7.8 7.7 7.6 7.5 7.4 7.3(metres)

Carriageway Cycleway FootwayFootpath

Max Min Max Min Max

Longitudinal Gradient 10% 1% 3% 1% 8%(general) (note 1) (note 2) (note 3) (note 1)

Longitudinal gradientof side road at

junction 5%(for first 6m from

main road channel)

Crossfall 3.3% 2.5% 2.5%

Notes:(1) increased gradients will be considered provided they are discussed

and agreed with the engineer at the planning application stagetogether with any special details (including surfacing) which may berequired.

(2) this gradient may be reduced to 0.67% if combined drainage andkerb blocks are used, except for block-paved roads.

(3) the gradient of cycleways may be increased to 5% for lengths up to100m, or 7% for lengths up to 30m.

4.3.8 Full size commercial vehicle turning heads are to be located at the endsof all culs de sac. The required dimensions are as follows:-

Figure 4.3.8 Turning Heads


PA G E 38JA N 96

Turning Heads:

3m

13m

9m

15m

7.3m 18m

9m

24m

6m

15m

53m

9m

25m

6m

4.3.9 Commercial estate layouts shall be such as to ensure that there are fullsize commercial vehicle turning facilities at least every 300m within thehighway system; for this purpose road junctions can provide the facility.

4.3.10 Kerbs will be pre-cast concrete 300mm x 150mm bull-nosed. Upstandsshall be:

150mm generally,6mm at footway crossings and12mm at vehicle accesses

Frequency

Kerbs


PA G E 39 JA N 96

4.4 LAYBYS

4.4.1 Parking lay-bys consist of multiples of 6m parking bays with entry and exitsplays tapered at 30°. The lay-by will be 2.5m wide between road channeland kerbline and should slope toward the carriageway at 2.5% grade.Footways or service margins are to be diverted around the lay-by.

Parking Lay-bys

Bus Lay-bys

2.5m

6.0m

30°

12m

3.0m

12m12m

4.4.2 Bus Lay-bys should cater for the largest public transport vehicle operatedin the neighbourhood of the development. They are to be 3m widebetween road channel and kerbline and are usually to be 12m long, butwhere frequent bus services are expected a longer length may berequired. Entry and exit splays shall be 12m long. Lay-bys should slopetowards the carriageway at 2.5% grade. Footways or service margins areto be diverted around the lay-by.

4.4.3 Information board lay-bys should be provided near the entrance(s) oflarger developments so that delivery drivers can find individualbusinesses. They are similar to the Bus Lay-by except that its lengthshould be 32m plus entry and exit splays of 12m.

Information

Board Lay-bys

Figure 4.4.1 Parking Layby

Figure 4.4.2 Bus Layby

4.5 TRAFFIC CALMING

4.5.1 The spacing of speed restraint measures is specified for each type of roadin Section 3. This spacing is to be measured as follows:-


PA G E 40JA N 96

Spacing of

Traffic Calming

Features

narrowing as a speed restraint measure

L L

L = distance between restraint measure

turning head Junction

3.5m

2.0m

illuminated bollard

lamp columnblock paviours

natural or simulatedstone setts

1 in 20

2m 4m 2m

4.5.2(i) Junction Treatment

Road junctions within a commercial estate are to be block paved with arumble strip formed from natural or simulated stone setts, as detailed inpara. 4.2.4 (ii). The following points should be noted:• there is to be a 150 mm kerb upstand throughout, except at

pedestrian crossing points • pedestrian refuges may well be required, as the crossing points may

not be at the narrowest part of the road.

Examples of

Traffic Calming

Features

Figure 4.5.1 Spacing of Traffic Calming Features

Figure 4.5.2(ii) Gateway entrances and Pedestrian Crossing PointsFigure 4.5.2(ii) Gateway entrances and Pedestrian Crossing Points


PA G E 41 JA N 96

concrete block paviours

Natural or simulated

stone settsIn loop road planter to be enclosed

in stone or brick wall, minimum height 300mm,with maximum height of planting 600mm

In cul de sac removable planters are to be provided(consult the engineer for details)

3.5m

150mm kerb upstand throughout

Traffic Calming

Features

6.0m

removable planters

3.5m 6.0m

2.5m

contrasting texture toremainder of road

2.0m2.0m

Figure 4.5.2(iii) Carriageway Width Restrictor

Figure 4.5.2(iv) Cul de sac Restrictor

4.6 CYCLEWAYS, FOOTWAYS,

FOOTPATHS AND VERGES

4.6.1 The crossfall of footways and verges is to be 2.5% towards thecarriageway. Cycleways and footpaths are either to be of balanced sectionor side hung with crossfalls of 2.5%. In general, the levels at the back of afootway should be parallel to the channel level.

4.6.2 Gradients for footpaths and footways are not normally to exceed 8%;however, increased gradients will be considered provided that they areagreed with the Engineer. Special details, including surfacing, may wellbe required.

4.6.3 The gradient for cycleways should not normally exceed 3%, but forlengths up to 100m it may be increased to 5%, and for up to 30m lengthsit should not exceed 7%. Steeper gradients will only be permitted forvery short lengths under difficult circumstances.

4.6.4 Edging to footways is to be laid with a 12mm upstand or flush with thesurface where the footway runs across public open space. A 150mm x50mm edging kerb will normally suffice, but where the edge of a footwayis within 1 metre of the top of an embankment, a full 250mm x 125mmbull-nosed kerb is to be provided with appropriate haunching andfoundations.

4.6.5 Edging to footpaths is to either be flush with the surface where water candrain to adjacent publicly maintained landscape areas, or a 12mmupstand where drainage is provided for the footpath.

4.6.6 Dropped crossings will be required at all road junctions. The crossingsshall be formed by dropping two standard kerbs (or the equivalent) to a6mm upstand with kerbs ramped on either side. These crossing pointsshould be located at the junction tangent points.

4.6.7 Where there is no known blind or partially-sighted pedestrian activity, thepedestrian crossing places will include a single row of buff colouredtactile paving slabs, adjacent to the dropped kerbs.

4.6.8 Where significant numbers of blind or partially-sighted pedestrians areexpected, the policy contained in the Department of Transport’sDisability Unit Circular 1/91 should be followed, in consultation with theEngineer.

4.6.9 Skewed crossings are confusing, so that “straight across” crossings shouldbe used wherever possible. Although this may cause pedestrian diversion,it will minimise the crossing distance for disabled pedestrians. If skewedcrossings are unavoidable, the alignment of the tactile surface is to besuch that they “point” to the opposite dropped kerbs.

4.6.10 Preformed cycle logos applied to the ground shall be provided so that atany point on the route at least one is visible, and also at points ofpedestrian access. The relevant traffic signs must be provided at each endof the route, and at all points where a vehicular carriageway is crossed.


PA G E 42JA N 96

Crossfalls

Gradient

Edging to

Footways and

Footpaths

Pedestrian

Crossing Points

Tactile Paving

and Blind and

Partially-sighted

Pedestrians

Cycle Markings

4.7 SURFACE WATER DRAINAGE

4.7.1 An adequate system of drains shall be provided for the collection anddisposal of surface water from the estate roads. The method of surfacewater disposal must be investigated at the outset with the Authorityconcerned. The developer will be required to give evidence that he has aright to discharge surface water at the proposed point of discharge, andthat he has secured satisfactory outfall arrangements. It must not beassumed that permission will automatically be given by the HighwayAuthority to make a connection to a highway drain in an adjoiningadopted County Road. Surface water from private land must beprevented from discharging on to the highway.

4.7.2 All maintainable highway drains shall be laid within the area of the estateroad and land that is to be adopted by the Highway Authority. TheHighway Authority will not adopt estate roads until the Water Authorityor its Agent has confirmed that the sewers within the estate have beenconstructed to their satisfaction and that they will be adopted by thatAuthority upon completion.

4.7.3 Soakaways are not normally acceptable as a road drainage outfall;however, they will be considered in special circumstances where it can bedemonstrated to the satisfaction of the Engineer that the soakage valueof the subsoil is capable of dealing with the surface water run-off in stormconditions.


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Developer’s

Obligations

Details of

drainage designSubsoil Drainage1) In areas of high water table a system of subsoil or French Drains shall be

provided to ensure that the water table is permanently reduced to a level of600mm below the carriageway formation level.

2) The water table level shall be determined by auguring boreholes as required bythe Engineer.

Pipe Sizes1) The size and gradient of surface water pipelines shall be calculated in

accordance with the Lloyd-Davies method as described in Road Note 35 (TRL),and the calculations as set out in its Table 1 shall be submitted for the approvalof the Engineer together with layout and detailed drawings.

2) The minimum diameter of a highway surface water drain shall be 150mm.Where pipes are laid with less than 1.2m cover under carriageways or 1.0m coverunder footways and verges, the pipes shall have concrete protection as describedin the Specification.

3) Self-cleansing gradients shall be provided to a velocity not less than0.75m/second.

4) Peak velocities above 6m/second require special attention with regard to energydissipation and grit scour, and if the pipe leads to an open -ended discharge,velocity at outfall should not be more than 3m/sec. unless energy dissipation isprovided.

Manhole PositionsOn all surface water pipelines less than 900mm in diameter a manhole shall beprovided:-

• at every change of gradient or alignment • at every change in size of pipeline • at the head of all pipelines • at every junction of pipelines (except individual gully and house connections) • at a maximum spacing of 90m.Outfalls

Open outfalls are to be approved by the National Rivers Authority; dischargevelocity shall not be greater than 3m/sec without the provision of energydissipation.

Gully PositionsAll gullies shall be positioned that:-1) the area draining to each road gully shall not exceed 200 square metres, and

that draining to each footpath gully shall not exceed 100 square metres 2) the spacing of gullies shall not exceed 50m in each channel on cambered roads

or the lower channel on side hung roads 3) where the channel gradient is steeper than 3.3% the spacing of gullies shall not

exceed 25m to avoid excessive velocities 4) the channel gradient shall not be flatter than 1% (0.66% with precast channels) 5) double gullies shall be provided at the low point on a concave channel profile

and at other low spots such as turning heads 6) at road junctions gullies should be sited upstream of the tangent points so that

they are not coincident with crossing points 7) where super-elevation is employed a gully should be sited just short of the point

at which adverse camber is removed 8) the maximum length of one gully connection shall be 13m 9) gullies should be located clear of private drives and aligned to avoid catching

cyclists wheels.Petrol Interceptors

Where petrol interceptors are required by the National Rivers Authority orSouth West Water, they are not to be placed in the Highway. The HighwayAuthority will not adopt petrol interceptors.

Design Notes1) The tables used for design shall be: “Tables for Hydraulic Design of Storm-

Drains, Sewers and Pipelines”, Hydraulics Research Paper No. 4 Fourth EditionHMSO 1983.

2) The ‘K’ value used shall be in accordance with Table 9, Road Note 35 SecondEdition TRL.

3) Tables setting out the rainfall of any specified duration and return period forspecified locations in Devon may be obtained from:-The Meteorological OfficeLondon Road, Bracknell, Berkshirequoting OS Grid Reference of the approximate centre of the drainage area.

4) Time of entry shall be taken as 2 minutes.5) Unless otherwise advised the design frequency shall be 2 years.6) Class of pipe shall be in accordance with “Simplified Tables of External Loads

on Buried Pipelines” (HMSO) and with “A Guide to Design Loadings for BuriedRigid Pipes” (HMSO 1983).


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4.8 MAINS AND SERVICES

4.8.1 Statutory Undertakers have a right to lay their apparatus within amaintainable highway or land which is prospectively a maintainablehighway. Their right to lay and maintain their apparatus is regulated bythe New Roads and Streetworks Act 1991. Within the meaning of this Actthe County Council is the Street Authority for maintainable orprospectively maintainable highways.

4.8.2 As well as making provision for pedestrian and vehicular movementscommercial roads provide routes for statutory and other servicesunderground. Those who provide such services must be consulted at anearly stage of design, their requirements co-ordinated in the design, andadequate provision made in the footway width for the anticipateddemand. Also, the siting of electricity sub-stations and gas governorsshould be considered at an early stage rather than as an afterthought.

4.8.3 Therefore, developers should provide space for services in the adoptedhighways (an exception to this is in paragraph 4.8.7). The provision ofmains and services is an integral part of the design and constructionprocesses, and discussions must take place with the statutory undertakersbefore plans are submitted for planning approval. A co-ordinated servicelayout must be provided prior to entering a Section 38 Agreement.

4.8.4 All services must be located underground. However, to minimiseinstallation and repair costs and the disruption that can be caused byrepairs, services, including the main sewers, should be laid outsidecarriageways, unless no other route is available e.g. in turning heads.Ducts across carriageways as required by Statutory Undertakers or forstreet lighting purposes are the only cases where services may be laid inthe carriageway. Mains and services should be suitably protected whenthere would be risks of damage from heavy vehicles. Developers shouldnote that:-(i) SEWERS must be laid in straight lines between manholes and these

should be sited in adopted areas (ii) HYDRANTS must be sited in easily accessible places after

consultation with the fire service.(iii) ELECTRICITY SUB-STATIONS, GAS GOVERNORS AND

TELEPHONE JUNCTION BOXES will require lorry access for bothinstallation and maintenance.

(iv) TELEPHONE LINES should be placed underground - distributionpoles should not be used.

4.8.5 Single lane carriageways and parking areas especially must be plannedwith the needs in mind of those utilities requiring jointing chambers,hydrants and link boxes, because operational vehicles need to be parkedclose to such access points whilst minimising risks of obstruction to trafficand ensuring that access to services is not obstructed.

4.8.6 The footway width of 2.5m will normally accommodate all services.However, greater widths may be required where, for instance,undertakers’ services may need to be upgraded.


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Legal Position

Careful Design

Services not to

be in the

Carriageway

Parking and

Access for

Maintenance

Services in the

Footway

4.8.7 It may be possible, with the agreement of the Statutory Undertakers, toplace some of the services beneath a landscaping strip to the rear of thefootway. This strip will not form part of the adopted highway, but wouldbe maintained (under the terms of a Planning Agreement) by thefrontagers, estate manager, or the like. The form of planting used in sucha strip should be discussed with the Statutory Undertakers.

4.9 STREET LIGHTING

4.9.1 Street lighting must be planned as integral part of the layout of roads,footpaths and underground services. Adequate provision is needed toincrease the sense of personal security, to reduce night time accidents,and to discourage crime and vandalism. Developers should liaise with theEngineer during the preparation of the scheme in order that theHighway Authority may be aware of what the developer is trying toachieve. When the road, footway, and footpath details have been agreedthe Highway Authority will provide details of the street lighting layoutrequired, which will show the number, siting and height of lamp columnsor brackets, and lamp type and wattage.

4.9.2 However, developers may choose columns or brackets from the HighwayAuthority’s list of approved equipment, a sample of which are shownbelow. Some locations have a style and colour of lamp columns of theirown, and these are to be used as appropriate. Street lighting equipmentshall be supplied and installed by the developer in accordance with therequirements of the Highway Authority’s Specification (Part 4 of thisGuide).


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Services could

be in a

Landscaping

Strip at the ear

of the Footway

Overall Design

Detailed Design

4.10 CUTTINGS AND EMBANKMENTS

4.10.1 The slopes of cuttings and embankments will generally be a maximum of1 in 1.5 for cuttings and 1 in 2 for embankments. However, steepercutting slopes may be acceptable if the submission is accompanied by anengineering geological assessment, and will, in any case, have to beapproved by the Engineer.

4.10.2 Other minimum dimensions and slopes are given below:-

Figure 4.10.2 Side Slopes


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Safe Slopes

600mm

1.0m to edgeof highway.

600mm

600mm

600mm

1.0m to footway or2.0m to edge of carriageway.where there is no footway

Embankment

600mm

1.0m to footway or1.5m to edge of carriageway.where there is no footway

600mm

600mm

600mm

1.0m to edge of highway.Cutting

4.11 HIGHWAY STRUCTURES

4.11.1 Where the required embankment and cutting slopes cannot be achieved,retaining walls must be provided.

4.11.2 Retaining walls and embankments that support a potential publichighway will be included in any highway adoption Agreement. Anyretaining wall which supports land above the highway will NOT beadopted.

4.11.3 Nonetheless, over and above the requirements of Section 167 of theHighways Act 1980, in developments associated with Section 38Agreements:• any retaining wall which supports land above the highway greater in

height than 1.0 metre and which is nearer than 1.5 times the height ofthe wall,

• any wall giving support to the highway that is greater in height than0.75 metre, and

• any bridge, underpass, subway or culvert which renders support to apublic highway

shall be submitted to the Highway Authority for Technical approval. (Fordetails, see Part 3, Section 1.9). It should be noted that, where a retainingwall is adoptable, timber crib construction is not acceptable.

4.11.4 Details of any vehicle guard rails, steps and ramps and their associatedhand-rails are also to be submitted.

4.12 ACCESS FOR FIRE APPLIANCES

4.12.1 If a fire breaks out in a building, fire appliances will need to get as closeto the building as practicable without delay. Access roads for fireappliances must therefore be included in the planning of all newbuilding developments. It is recommended that the proposals for accessfor fire appliances are verified with the Fire and Rescue Service duringthe early stages of planning the development.


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Retaining Walls

Adoption of

Retaining Walls

Technical

Approval of

Structures

Adjacent to the

Highway

General Layout

of Fire

Appliance

Access

4.12.2 In preparing any scheme, the developer is to follow the advice given bythe Devon Fire and Rescue Service, who can be consulted at theaddresses shown below:-

Fire and Rescue Service, Brigade HeadquartersThe KnowleClyst St. GeorgeExeter EX3 0NW tel 01392 873711

Fire and Rescue Service, East Division HeadquartersThe KnowleClyst St. GeorgeExeter EX3 0NJ tel 01392 873711

Fire and Rescue Service, North Division HeadquartersNorth RoadPiltonBarnstaple EX31 1PA tel 01271 71515

Fire and Rescue Service, South Division HeadquartersNewton RoadTorquay TQ2 4BY tel 01803 613831

Fire and Rescue Service, West Division HeadquartersGlen RoadPlymptonPlymouth PL7 3XT tel 01752 330131


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Specific

Requirements

Contact

Addresses

Highways in Residential and Commercial Estates · Highways in Residential and Commercial Estates...

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