DMRB VOLUME 8 SECTION 4 PART 6 - Standards …

1 November 2003 DESIGN MANUAL FOR ROADS AND BRIDGESVOLUME 8 TRAFFIC SIGNS ANDLIGHTINGSECTION 4 TRAFFIC MANAGEMENTAT ROADWORKSPART 6TA 92/03 crossover AND CHANGEOVERDESIGNSUMMARYThis document provides guidance to assist designers oftemporary traffic management systems that includechangeovers and crossovers. Geometric and non-geometric advice is FOR existing Contents pages for VOLUME new Contents pages for VOLUME 8 datedNovember TA 92/03 into VOLUME 8, SECTION 4, part Advice Note supersedes Chapter 5 ofTA 45/85 ( dmrb ). archive this sheet as : A quarterly index with a full set of VolumeContents Pages is available separately from TheStationery Office 92/03 crossover and ChangeoverDesignSummary:This document provides guidance to assist designers of temporary trafficmanagement systems that include changeovers and crossovers. Geometricand non-geometric advice is MANUAL FOR ROADS AND BRIDGESTHE HIGHWAYS AGENCYSCOTTISH EXECUTIVEWELSH ASSEMBLY GOVERNMENTLLYWODRAETH CYNULLIAD CYMRUTHE DEPARTMENT FOR REGIONAL DEVELOPMENTNORTHERN IRELANDV olume 8 SECTION 4 part 6 TA 92/03 November 2003 REGISTRATION OF AMENDMENTSA mendPage NoSignature & Date ofAmendPage NoSignature & Date ofNoincorporation ofNoincorporation ofamendmentsamendmentsRegistration of AmendmentsVolume 8 SECTION 4 part 6 TA 92/03 November 2003 REGISTRATION OF AMENDMENTSA mendPage NoSignature & Date ofAmendPage NoSignature & Date ofNoincorporation ofNoincorporation ofamendmentsamendmentsRegistration of AmendmentsVOLUME 8 TRAFFIC SIGNS ANDLIGHTINGSECTION 4 TRAFFIC MANAGEMENTAT ROADWORKSPART 6TA 92/03 crossover AND Design6 Sizing the AGeometric Design TablesDESIGN MANUAL FOR ROADS AND BRIDGESN ovember

2 2003 VOLUME 8 SECTION 4 part 6 TA 92/03 November 20031/1 Chapter 1 Introduction1. Advice Note should be used to determinethe location and design of crossovers and changeoversin temporary traffic management Advice Note supersedes Chapter 5 ofTA 45 [ dmrb ]. has highlighted the need for advice toprovide consistency in the design and layout ofcrossovers on dual carriageway roads and of this document should ensure appropriatelocations, and satisfactory horizontal and verticaldesign. crossover location, and more particularlycrossover length, must not be dictated by using anexisting central reserve gap that is too short for themandatory temporary speed limit. A well-designedcrossover will minimise vehicle braking and queuing,therefore reducing the risk of nose-to-tail design of a crossover is a balance betweenavailable locations, economical construction cost andconvenience to road users.

3 As crossovers form part of atemporary and often changing situation, attentionshould be given not only to the known situation andprogramme for the Works, but also to the possibility ofunplanned changes or basis of the design recommendations in thisAdvice Note allows for a reduction in normal drivercomfort within the design while maintaining acceptablelimits for sideways acceleration. Temporary trafficmanagement arrangements are prominently signed andconsequently driver concentration is heightened. In thissituation drivers are able to tolerate a tighter geometricdesign than can be accepted in a non-roadworkssituation on the assumption that the chosen designspeed is consistent with the adopted temporarymandatory speed construction within the central reserveshould normally be retained for future use, unless thereis justification for removal at the completion of theWorks where retention creates a safety hazard oraffects the Advice Note sets out guidance for thelocation and geometric layout of crossovers andchangeovers on dual carriageway roads and supplements the advice given in Chapter 8 (1991)paragraph of the Traffic Signs Manual [TSM].

4 Asoftware macro is provided (Chapter 6) to assistdesigners in sizing a Advice Note also highlights features, suchas lighting, drainage, pavement and non-motorised userissues that require consideration in the design andoperation of any of Existing crossover to re-use of an existing crossover site adesign assessment is required, even where it hasoperated without problems in the past. There is norequirement to assess any existing crossover site untilplans arise to re-use it. In the event that a crossover sitefails this assessment, guidance is given in Roads and Network Improvement When designing new roads or networkimprovement schemes it is not usually desirable toprovide crossover sites for the purposes of futuremaintenance works. However, part of the designprocess for a new road or improvement scheme is toinclude consideration of future maintenance needs.

5 ThisAdvice Note should be taken into account whenidentifying lengths of central reserve which could bedesigned to contain the minimum of equipment to allowfor the construction of crossovers, at a later date. In allcases the maintaining organisation should be consultedthrough the Overseeing 78 [ dmrb ] gives mandatoryrequirements for crossovers at As-built drawings for the Works should indicatethe assumed design speed used in the design of acrossover. This will assist at a later date when crossoversites are considered for 8 SECTION 4 part 6 TA 92/03 November 20031/2 Chapter 1 IntroductionExplanatory This Advice Note applies to all crossovers, butthe terminology used is applicable to the first crossoverin a temporary traffic management This Advice Note should be used forthwith on allschemes for the construction, improvement andmaintenance of trunk roads, including motorways,currently being prepared provided that, in the opinionof the Overseeing Organisation, this would not result insignificant additional expense or delay progress.

6 DesignOrganisations should confirm its application toparticular schemes with the Overseeing this is confirmed, the contract documents for theWorks should be written to reference this Advice changeover is a change of lanes introduced todivert traffic within an existing carriageway, includingthe hard shoulder. A changeover is normally associatedwith temporary works where one or more lanes areclosed. It may occur after the traffic has been mergedinto fewer lanes than the permanent situation. Nofurther reference is made to changeovers in this AdviceNote as the criteria for crossovers apply equally crossover is where one or more lanes on a dualcarriageway or motorway are diverted onto theopposing carriageway. This is normally where acontraflow situation is required to carry out Works onthe primary carriageway. crossover length is shown inFigure 1.

7 Note that a second crossover is needed toreturn to the primary carriageway. crossover site is thepaved area within the central reserve used as part of To differentiate between existing horizontalalignment and the new horizontal curves introduced toform the crossover : bend is used to describe a horizontal radius in theexisting road alignment; curve is used to describe the crossover S shape; entry curve is used to describe the first curve ofthe S shape; exit curve is used to describe the second curve ofthe S shape; non-assisting refers to superelevation that assiststraffic in the non-works situation but adverselyaffects traffic through a crossover alignment is measured on thecentreline of the temporary 1: Typical layout of a crossoverVolume 8 SECTION 4 part 6 TA 92/03 November 2003 Chapter 1 Introduction1 shift is used to describe the sidewayschange in position of a vehicle from one carriageway tothe opposite The term Large Goods Vehicles (LGV) is usedin this document to identify those vehicles (defined asover tones gross weight) classified as LGVs forlicensing purposes in accordance with Europeanharmonisation of factor is used to describe thepossibility of overturning, particularly in relation tolarge vehicles.

8 Overturning depends on the height of thecentre of gravity relative to the width of the vehicle strack. The motions which might cause a large vehicle toroll over depend very greatly on the characteristics(dimensions, loading and suspension) of the individualvehicle and the manoeuvres being carried out, butallowances have been made within the guidance givenin this Advice crossover site: paved area within thecentral reserve that is to be built, or already exists, butwill not be used again after the completion of crossover site: paved area within thecentral reserve that is to be built, or already exists, andwill be closed but not removed at the completion of theWorks, allowing future crossover : A crossover that carriestraffic in only one direction at a time, but which may bereversed during the Works to carry traffic in theopposite crossover : A crossover that carriestraffic in only one direction at a time, and which mustnot be reversed during the carriageway: The carriageway onwhich the Works are being carried out, and thereforethat from which the crossover carriageway: The carriagewayopposite to the primary : The maintenance or improvementproject that requires the use of a 8 SECTION 4 part 6 TA 92/03 November 20032/1 Chapter 2 Traffic Management2.

9 TRAFFIC requirements for traffic managementcontractors working on high speed roads are given inthe Specification for Highway Works (SHW). management system designs shall be inaccordance with the TSM Chapter 8 and the DesignManual for Roads and Bridges ( dmrb ). Particularreference to TA 64 [ dmrb ] is cameras are an effective way of reducingspeeds within temporary traffic management the police are willing to operate the cameras,then their provision should be considered for inclusionin the contract requirements. The OverseeingOrganisation should be consulted to determine currentpolicy before a decision to use cameras is 8 SECTION 4 part 6 TA 92/03 November 20033/1 Chapter 3 Planning3. responsibility for the design of the trafficmanagement system shall be as stated in the contractdocuments for the of the status of the designer of thetraffic management system, the OverseeingOrganisation and their Agents should ensure that dueconsideration is given in the preparation of the Works tothe practicality of achieving crossover designs thatconform to this Advice Note, prior to entering into acontract for the Works.

10 The overriding principle is thatcrossovers should be constructed to comply with theproposed temporary mandatory speed limit for choice of location for a crossover is the mostcritical factor affecting both the safety in use andconstruction costs for the crossover site. It will alsohave a significant bearing on the safety, capacity anddelays for the whole traffic management a crossover should be located away fromjunctions, on a straight and relatively flat SECTION of thecarriageway, with street lighting and minimal centralreserve aim is to build a safe crossover while stillallowing the Works to be constructed in a cost-effectivemanner. Every effort should be made to find the bestpossible practical location that is appropriate to aparticular factors have to be considered whenchoosing the location of any crossover . In some casesfinding a fully suitable location will not be possible andit will be necessary to use a location which does nothave an ideal combination of all relevant factors.