A358 Taunton to Southfields Dualling Scheme Technical Appraisal Report Updated February 2018 Technical Appraisal Report – List of Amendments The following changes have been made since the version issued in January 2018. Corrections Version Page Paragraph/Table/Figure Comment January 2018 165 Table 8.5 The column “Orange option (via J25A) - Difference (min:sec)” has been reformatted to show times in minutes and seconds. The previous version had been formatted to show percentages in error. January 2018 212 Appendix B2- Shortlisted Junctions had been positioned Options incorrectly, the map has been updated to reflect correct positions. February 2018 206 Paragraph 17.1.1 BCR description changed from good to high. Good was stated in error. A358 Taunton to Southfields Table of Contents Executive Summary 1 1. Introduction 7 1.1. Background to this report 7 1.2. Purpose of the report 7 1.3. Wider context 8 1.4. Scheme overview 10 1.5. Scheme description 11 1.6. Report structure 11 2. Planning Brief 14 2.1. Scheme objectives 14 2.2. Client scheme requirements 14 2.3. Highways England organisational objectives 15 3. Existing conditions 16 3.1. Introduction 16 3.2. Description of the locality 16 3.3. Existing highway network 20 3.4. Traffic data 23 3.5. Accidents and journey time reliability 28 3.6. Topography, land use, property and industry 32 3.7. Climate 33 3.8. Drainage 35 3.9. Geology 36 3.10. Mining 38 3.11. Public utilities 38 3.12. Environment 41 3.13. Accessibility 45 3.14. Integration 46 3.15. Maintenance and repair statement 49 4. Planning factors 51 4.1. Legislation and guidance 51 4.2. Local policy 59 5. Description of route options 66 5.1. Introduction 66 5.2. Options Identification 66 5.3. Development of route options 68 5.4. Northern routes in detail 73 5.5. Central routes in detail 77 5.6. Southern routes in detail 88 6. Options Sifting 92 Technical Appraisal Report Page i A358 Taunton to Southfields 6.1. Initial sifting 92 6.2. Phase 1 sift 96 6.3. Phase 2 sift - Economic growth, managerial, financial and commercial 112 6.4. Development and assessment of options 129 7. Shortlisted options 137 7.1. Pink option 137 7.2. Blue option 142 7.3. Orange option 146 8. Traffic analysis 152 8.1. Traffic data 152 8.2. Traffic analysis methodology 153 8.3. Traffic Model 157 8.4. Summary of traffic assessment 160 9. Road layout and standards 175 9.1. Standards used 175 9.2. Road geometry 175 9.3. Cross sections 175 9.4. Junction strategy: location and layout 176 10. Economic assessment 177 10.1. Application of TUBA/COBA 177 10.2. Accident savings 182 10.3. Results of the economic appraisal 183 11. Safety assessment 185 11.1. Impact on road user – strategic safety action plan 185 11.2. Buildability 186 12. Environmental appraisal 188 12.1. Introduction 188 12.2. Consultation with statutory bodies 188 12.3. Noise 188 12.4. Air quality 189 12.5. Greenhouse gases 191 12.6. Landscape 191 12.7. Historic environment 192 12.8. Biodiversity 193 12.9. Water environment 193 13. Social impact appraisal 195 13.1. Social appraisal 195 14. Engagement with stakeholders 197 14.1. Identifying and engaging with stakeholders 197 Technical Appraisal Report Page ii A358 Taunton to Southfields 14.2. Information provision – stakeholder workshops 198 14.3. Local authority communications and community engagement meeting 199 14.4. SoCC development group meetings 199 14.5. Communications working group 200 14.6. 2017 Public Consultation 200 14.7. Further engagement 201 15. Appraisal summary 202 15.1. Appraisal Summary Tables (ASTs) 202 15.2. Comparison of options 202 16. Programme 205 17. Conclusions and recommendations 206 17.1. Options for public consultation 206 Appendices 207 Appendix A Glossary 207 Appendix B Route Options and Environmental Constraints Plan 211 Appendix C Sift scoring mechanism 215 Appendix D Appraisal Summary Tables 218 Technical Appraisal Report Page iii A358 Taunton to Southfields Executive Summary Introduction The A358 Taunton to Southfields scheme is part of a programme of improvements planned along the A303 / A358 corridor aimed at improving connectivity between London and the south east and the south west. The programme, as set out in the Government’s Road Investment Strategy (www.gov.uk/government/collections/road- investment-strategy), will create a continuous high quality dual carriageway along the route by upgrading all the existing single carriageway sections. The A358 is located in the county of Somerset in the Taunton Deane and South Somerset Districts. It passes through a predominantly rural area consisting mainly of arable and livestock farmland and through the civil parishes of Ruishton, Thornfalcon, West Hatch, Hatch Beauchamp, Bickenhall, Ashill and Horton. The A358 and A303 route suffers traffic congestion and poor journey time reliability, particularly at peak holiday times in the summer months and at weekends when many are journeying to and from the south west. The upgrades to the A358 corridor will help alleviate these issues. Purpose and Context of the Technical Appraisal Report This Technical Appraisal Report (TAR) reports on the existing problems and constraints along the A358 between Taunton and Southfields Roundabout on the A303, near Ilminster. The TAR reports on potential solutions for this A358 scheme, detailing the identification, sifting and appraisal of route options to determine which should be taken forward for Public Consultation. This TAR is an update of the previous version dated March 2017 (published April 2017), published at the time of the initial public consultation held between 28 March and 16 July 2017. Much of the content is the same as the previous version, but some revisions have been made, including a more comprehensive discussion of the long list of 28 potential options for upgrading the A358 (Section 5) and how these were narrowed down to a short list of 4 options (Section 6). These 4 options that were then appraised in greater detail prior to a single route option being taken forward for the 2017 consultation. A strong feedback theme from the initial consultation was a wish to see more options for connecting with the M5, for providing traffic relief for Henlade, and for connecting more directly with the future ‘Nexus 25’ development, a major new employment site planned in the south-east quadrant of the existing junction 25. Highways England has carefully considered this feedback and has made the decision that it would be beneficial to reconsult and seek views on more options for routing the upgraded A358 past Henlade, with accompanying options for connecting the M5, before making a decision on the choice of preferred route. 3 options are being put forward for further consultation as summarised below. Technical Appraisal Report Page 1 A358 Taunton to Southfields Options for reconsultation From the 4 options shortlisted in the 2017 TAR (dated March 2017), one was subsequently discounted because it would have significantly greater environmental impacts on landscape and biodiversity than the other 3 options. Those 3 options are now being put forward for consultation. The 3 options being put forward for consultation are the Pink option, Blue option and the Orange option, as shown below on Figure 0.1. Figure 0.1 Option routes Source: MMSJV. This Map is based upon Ordnance Survey material with the permission of Ordnance Survey on behalf of the Controller of Her Majesty's Stationery Office © Crown copyright. Unauthorised reproduction infringes Crown copyright and may lead to prosecution or civil proceedings. Highways England 100030649 2016. Description of Options Pink option Starting from the west, the Pink option commences from a new junction on the M5 approximately 1.2 miles (2 kilometres) south of junction 25. South-facing slip roads from the M5 would combine to become the new dual carriageway, which runs eastwards and north of Stoke Hill. Here a limited-movement junction is proposed with east-facing slip road connections to the new road which would allow traffic to travel between the new A358 and junction 25 via a new 0.9 mile (1.5 kilometre) dual carriageway link past the planned Nexus 25 site. Technical Appraisal Report Page 2 A358 Taunton to Southfields The route then continues in a south-easterly direction to Mattock’s Tree Green where an all-movement, grade-separated junction is proposed which would allow access to Hatch Beauchamp, Henlade and surrounding communities, and A378. The proposed route would then follow the existing A358 to Southfields Roundabout enabling the existing road to be upgraded from a single to a dual carriageway. An additional all-movement grade separated junction is proposed near to Ashill to access Ashill, Ilton and surrounding communities. The total length of the Pink option is 9 miles (14.6 kilometres), plus the 0.9 miles (1.5 kilometres) spur leading to M5 junction 25. Blue option Like the Pink option, the Blue option commences at the M5 approximately 1.2 miles (2 kilometres) south of junction 25 and runs eastwards on a more southerly alignment. At Stoke Hill a junction is proposed similar to that with the Pink option which would allow traffic to travel between the road and junction 25 via a new 1.2 miles (2 kilometres) dual carriageway link past the planned Nexus 25 site. The road would then continue in a south easterly direction to West Hatch Lane, where an all-movement, grade-separated junction is proposed which would allow access to Hatch Beauchamp, Henlade and surrounding communities, and A378. This option is identical to the Pink option from this point onwards to Southfields Roundabout. The total length of the Blue option is 8.7 miles (14.1 kilometres), plus the 1.2 miles (2 kilometres) spur leading to M5 junction 25.