Welsh Assembly Government Transport Wales New M4 Project - Magor to Castleton Junction Strategy Review April 2006 This report takes into account the particular instructions and requirements of our client. It is not intended for and should not be relied upon by any third party and no responsibility is undertaken to any third Ove Arup & Partners Ltd party 4 Pierhead Street, Capital Waterside, Cardiff CF10 4QP Tel +44 (0)29 2047 3727 Fax +44 (0)29 2047 2277 www.arup.com Job number 117300 1 Welsh Assembly Government Transport Wales New M4 Project - Magor to Castleton Junction Strategy Review Contents Page 1 INTRODUCTION 1 2 OPTIONS CONSIDERED 2 2.1 Intermediate Junction Options 2 2.2 Direct Link To A449 2 2.3 Eastern Junction Connecting into Nash Road and Meadows Road 3 2.4 Eastern Junction Connecting into Meadows Road Only 4 2.5 Eastern Junction Connecting into Meadows Road with a Possible Link to Corporation Road 4 2.6 Western Junction Connecting to A48 East of LG Factory 5 2.7 Western Junction with Connection to the A48 via Duffryn Link Road 6 3 TRAFFIC ASSESSMENT OF JUNCTION OPTIONS 7 3.1 Interim Traffic Model 7 3.2 No Intermediate Junctions 8 3.3 Eastern Junction Connecting into Meadows Road Only 8 3.4 Eastern Junction Connecting into Meadows Road with a Possible Link to Corporation Road 9 3.5 Eastern Junction Connecting into Meadows Road with a Possible Link to Corporation Road and Western Connection to A48 via Duffryn Link Road 9 3.6 Comments on Traffic Assessments 10 3.7 Initial Assessment of the Impact of Tolling the New M4 10 4 ECONOMIC EVAULATION 12 4.1 Basis of Transport User Benefit Appraisal (TUBA) 12 4.2 Assumptions Used in TUBA Evaluation 12 4.3 Output of TUBA 12 5 JUNCTION STRATEGY: OVERALL SUMMARY 14 J:\117000\117300-00\4 INT PROJ DATA\4-50 REPORTS\4-50-18 JUNCTION Ove Arup & Partners Ltd STRATEGY REVIEW\0002 JUNCTION STRATEGY REVIEW FINAL.DOC Final : April 2006 06/6866 2 Welsh Assembly Government Transport Wales New M4 Project - Magor to Castleton Junction Strategy Review Figures Figure 1.1 Illustrative Magor/Rogiet Interchange and Magor Junction Figure 1.2 Illustrative Castleton Interchange and Western Intermediate Junction Figure 2.1 Illustrative Eastern Intermediate Junction Figure 3.1 2013 and 2028 Traffic Forecasts with No Intermediate Junction on New M4 Figure 3.2 2013 and 2028 Traffic Forecasts with Eastern Intermediate Junction on New M4 Connecting into Meadows Road Figure 3.3 2013 and 2028 Traffic Forecasts with Eastern Intermediate Junction on New M4 Connecting into Meadows Rd with a Possible Link to Corporation Rd Figure 3.4 2013 and 2028 Traffic Forecasts with Eastern Intermediate Junction on New M4 Connecting into Meadows Rd with a Possible Link to Corporation Rd and Western Connection to A48 Appendix A Figure A.1 Direct Link to A449 Figure A.2 Eastern Junction Connecting into Nash Road and Meadows Road Figure A.3 Eastern Junction Connecting into Meadows Road Only Figure A.4 Eastern Junction Connecting into Meadows Road with a Possible Link to Corporation Road Figure A.5 Western Junction Connecting To A48 East of LG Factory Figure A.6 Western Junction Connecting To A48 via Duffryn Link Road Figures Figure 1 Figure Description J:\117000\117300-00\4 INT PROJ DATA\4-50 REPORTS\4-50-18 JUNCTION Ove Arup & Partners Ltd STRATEGY REVIEW\0002 JUNCTION STRATEGY REVIEW FINAL.DOC Final : April 2006 06/6866 3 Transport Wales Welsh Assembly Government New M4 Project - Magor to Castleton Junction Strategy Review 1 INTRODUCTION The Business Case for the New M4 will need to take into account possible locations for junctions. Preliminary consultations with Newport City Council and Monmouthshire County Council have set the scene in terms of land use development plans. At Magor - Rogiet and Castleton, free flowing interchanges have been developed. At Magor - Rogiet, value engineering developments have led to revisions to the details presented at Public Consultation (Autumn 1994) and necessitated a change to the published route corridor. The revised Magor - Rogiet Interchange arrangement incorporates west-facing slip roads linking the New M4 to the B4245 to the west of Magor. The previously published Castleton Interchange arrangement and the revised Magor - Rogiet arrangement have been included as preferred proposals in this junction strategy review, although it should be noted that further value engineering work is planned for both interchanges. It is planned to present the preferred interchange arrangements to the public and other stakeholders as part of the forthcoming Public Information Exhibitions; they are shown diagrammatically in Figures 1.1 and 1.2. This report summarises a review of options for intermediate junctions along the New M4. The review has broadly covered the following: general engineering feasibility related to technical standards and good practice guidance; traffic operations with particular reference to use of the New M4 and relief to the existing M4; comparative performance of options in terms of Transport Users Benefit Appraisal (TUBA); and an initial assessment of the impact of tolling of the New M4. The review has focussed mainly on traffic operations and route choice. In considering the potential location for intermediate junctions, general consideration has been given to environmental and economic issues. In particular, efforts have been made to minimise the impact of intermediate junctions on the Gwent Levels Site of Special Scientific Interest (SSSI). For further information, reference should be made to the Preferred Route Review Report prepared by Arup and dated April 2006. Following the appointment of a Financial Advisor by the Welsh Assembly Government, an Outline Business Case is to be developed for the New M4 Project. As part of this process, it is anticipated that there will be further development of the junction strategy. In parallel with the development of the junction strategy, studies are on-going in relation to associated measures that may be adopted along the existing M4 corridor in order to encourage greater accessibility and travel choice. Such measures have yet to be formulated and hence are not considered as part of this current review of junction strategy for the New M4. J:\117000\117300-00\4 INT PROJ DATA\4-50 REPORTS\4-50-18 JUNCTION Page 1 Ove Arup & Partners Ltd STRATEGY REVIEW\0002 JUNCTION STRATEGY REVIEW FINAL.DOC Final : April 2006 06/6866 4 Transport Wales Welsh Assembly Government New M4 Project - Magor to Castleton Junction Strategy Review 2 OPTIONS CONSIDERED 2.1 Intermediate Junction Options In order to conduct a broad review, the following intermediate junction options were initially considered in terms of alignment, physical constraints and design standards: A link directly to the A449 north of the existing M4 Junction 24, from a grade separated junction on the New M4 to the south of the Corus Steelworks as illustrated in Figure A.1 in Appendix A; The previously proposed eastern junction connecting to Nash Road and Meadows Road (see Figure A.2 in Appendix A); A modification of the previously proposed eastern junction without a through link along Nash Road (see Figure A.3 in Appendix A); A modification of the previously proposed eastern junction without a through link along Nash Road, but with a possible link to Corporation Road (see Figure A.4 in Appendix A); A link to the A48 west of Newport via an existing industrial estate road from a junction on the New M4 immediately to the east of the LG electronics factory (see Figure A.5 in Appendix A); and A link to the A48 via the Duffryn Link Road (see Figure A.6 in Appendix A). The characteristics of each of the above options are described below. 2.2 Direct Link To A449 This option commences with a grade-separated junction on the New M4 to the south of the Corus steelworks. This junction would be situated within the Gwent Levels Site of Special Scientific Interest (SSSI). The route runs at high level on the west side of Monks’ Ditch through Newport’s Eastern Expansion Area and crosses the existing dual-carriageway steelworks access road. North of this road, the alignment then drops to ground level, before rising again to cross over the existing railway lines running along the northern boundary of the Works. Beyond the railway, there are two possible routes. The eastern route lies in open farmland and skirts the village of Llanwern. The western route swings to the west and crosses through the village and proposed development land, before turning north to cross over Cog Hill. North of Cog Hill, the routes follow the same line and enter an extended viaduct structure over the A48 Newport Southern Distributor Road (SDR), the western side of the M4 Junction 24 Coldra gyratory and the motorway. The route then turns to the north-east to link with the A449. Links between the A449 and the Coldra junction would be maintained by new south-facing slip roads. The purpose of the route would be to provide a direct link between the A449 and the New M4 south of Newport. This is a strategic route; as such, no connections are provided off it to the remainder of the highway network. It is envisaged that the following structures would be required: Bridges at junction with New M4; Retaining walls alongside Monks’ Ditch Bridge over Steelworks Access Road; Two bridges over railway lines; J:\117000\117300-00\4 INT PROJ DATA\4-50 REPORTS\4-50-18 JUNCTION Page 2 Ove Arup & Partners Ltd STRATEGY REVIEW\0002 JUNCTION STRATEGY REVIEW FINAL.DOC Final : April 2006 06/6866 5 Transport Wales Welsh Assembly Government New M4 Project - Magor to Castleton Junction Strategy Review West route – Bridge over Station Road; West route – Bridge over Cog Hill; East route – Bridge over side road between Llanwern and Wilcrick; East route – Access bridge over the A449; East route – Bridge over Langstone Lane; Bridge/fly-over at Coldra.