ERA - Highways Agency

Web DAS v1.5::View Internal DeparturePage 1 of 6ID 60292Owning AgentAgent's Ref/TitleStatusForm Of ContractProject SponsorSpecialist SubmissionPointXWSAC - W.S Atkins Consultants LtdAtkins - Highways & Transportation - M4 M5 HSR - 5085236/400/D/100 PavementERAApproved with commentsOtherCameron, RobertBrown, SandraPIN Code 503624 - DEV M4 J19 TO 20 & M5 J15 TO 17Standard HD 24/06 - Traffic Assessment : Design, Road Pavement, DMRB Vol 07 Section 2Year Of Issue 2006Clause/ParagraphAdded ValueInnovationConfidentialDeparture Summary2.15 Standard design traffic calculation for new construction11 - 100 KgfedcgfedcAtkins - Highways & Transportation - M4 M5 HSR - 5085236/400/D/100 PavementERA The departure relates to the traffic assessment used to derive the designtraffic used to design the new pavement.Location(s) Structure Key LocationSubmission Details15.1 SubmissionM4 ERA01 West -Start chainage 44300; Finishchainage 44400M4 ERA02 West - Start chainage 45180; Finishchainage 45280M4 ERA03 West - Start chainage 46035; Finishchainage 46135M4 ERA04 East - Start chainage 46005; Finishchainage 45905M4 ERA05 East - Start chainage 45150; Finishchainage 45050M4 ERA06 East - Start chainage 44415; Finishchainage 44315M4 ERA07 East - Start chainage 43115; Finishchainage 43015M5 ERA03 South - Start chainage 56240; Finishchainage 56340M5 ERA04 South - Start chainage 57270; Finishchainage 57370M5 ERA06 North - Start chainage 56985; Finishchainage 56885M5 ERA07 North - Start chainage 56420; Finishchainage 56320The standard HD24/06 para2.15 states that all new carriageway constructionincluding hardshoulders should be designed to the same standard as the heaviestloaded lane.The Emergency Refuge Area is not intended to be a running lane or hardshoulder.It would not be economic or sustainable to design it to the same standard as theheaviest loaded lane. It will only take a small fraction of the design traffic as theheaviest loaded lane.http://webdas/departure/dispatch.aspx?verb=read&context=maindetails&id=6029221/01/2011

Web DAS v1.5::View Internal DeparturePage 4 of 6excavation and quantities involved would not be reduced.16.2.v BudgetThis departure will offer savings in the cost of materials due to the fact that boundmaterials are more expensive than unbound materials.16.2.vi EnvironmentalThis departure will over a reduction in the carbon footprint for the materials used.(Unbound materials have a lower carbon footprint than bound materials).16.2.vii InnovationThis departure is innovative insofar that it challenges the traffic assessmentmethods from HD24/06 being used for an emergency refuge area with a morepragmatic approach.16.2.viii Durability / MaintenanceThe durability and maintenance of the ERA should not be adversely affected bythis departure.16.2.ix Network AvailabilityThis departure will have a comparable impact on network availability to a fullycompliant design.16.3 Risks:16.3.i Safety (road users)This departure does not have any adverse impact on road users. The provision ofan ERA has a positive benefit as part of a managed motorway project.16.3.ii Safety (construction and maintenance)This departure does not have any adverse benefit on construction. ERAs will havea thin surface course system where appropriate to avoid the need to be resurfacedwhen the main carriageway is maintained.16.3.iii TechnicalThis departure challenges the standard HD24/06 for traffic assessment as notappropriate for an ERA and proposes a more pragmatic design traffic loading.16.3.iv ProgrammeThis departure would not necessarily offer any programme saving as theexcavation and quantities involved would not be reduced.16.3.v BudgetThis departure will offer savings in the cost of materials due to the bound materialsbeing more expensive than unbound materials.16.3.vi EnvironmentalThis departure will over a reduction in the carbon footprint for the materials used.(Unbound materials have a lower carbon footprint than bound materials).16.3.vii Innovationhttp://webdas/departure/dispatch.aspx?verb=read&context=maindetails&id=6029221/01/2011

Web DAS v1.5::View Internal DeparturePage 5 of 6This departure is innovative insofar that it challenges the traffic assessmentmethods from HD24/06 being used for an emergency refuge area with a morepragmatic approach.16.3.viii Durability / MaintenanceThe durability and maintenance of the ERA should not be adversely affected bythis departure.16.3.ix Network AvailabilityThis departure will have a comparable impact on network availability to a fullycompliant design.16.4 Mitigation:The ERAs will be designed to have a compatible sub-base layer to the adjacentmain carriageway to ensure the continuity of sub-base drainage path. Thelongitudinal joints will comply with Cl 903.21.16.5 Overall Justification:16.5.i Reasons why the Benefits (16.1) outweigh the Impacts (16.2)The benefits reflect a fit for purpose design that is cost effective compared to a fullycompliant design that is less cost effective. There are no significant impacts.16.5.ii Reasons why the Risks (16.3) after Mitigation (16.4) are ALARPThe risks have been designed out (longitudinal joint location and drainage of thesub-base layer). Therefore the risks are as low as reasonable practicable.16.5.iii Compatibility with adjacent roadsConsultant CommentsSSR Comments/DecisionThe surface course will be TSCS, The longitudinal joint will be positioned such thatit does complies with Cl 903.21. The sub-base layer of the ERA will match thedepth of the existing carriageway sub-base level.1. This Departure application seeks to design ERAs to a lesser trafficthan the mainline (5msa).2. The mainline traffic has been estimated as greater than 80msa.3. The design shows that the unbound subbase will be thickened toensure continuity of drainage against the new construction.4. This Departure is approved subject to the following comments:5. All other requirements for lay-bys given in HD26 must be compliedwith.http://webdas/departure/dispatch.aspx?verb=read&context=maindetails&id=6029221/01/2011

Web DAS v1.5::View Internal DeparturePage 6 of 66. If the ERA is to be surfaced using Thin Surface Course, it mustincorporate a fuel resisting binderOD CommentsDonna JamesPavement Design and Materials Team Leader13 th July 2010Attachments File Name Description5085236_DR_DP_6000_001.pdf Location Plan (sheet 1 of 7)5085236_DR_DP_6000_002.pdf Location Plan (sheet 2 of 7)5085236_DR_DP_6000_003.pdf Location Plan (sheet 3 of 7)5085236_DR_DP_6000_004.pdf Location Plan (sheet 4 of 7)5085236_DR_DP_6000_005.pdf Location Plan (sheet 5 of 7)5085236_DR_DP_6000_006.pdf Location Plan (sheet 6 of 7)5085236_DR_DP_6000_007.pdf Location Plan (sheet 7 of 7)5085236-DR-GL-0100-055.pdfDrawing number5085236/DR/GL/0100/055 -M4 East ERA01 and ERA06http://webdas/departure/dispatch.aspx?verb=read&context=maindetails&id=6029221/01/2011