A428 Black Cat to Caxton Gibbet Improvements

A428 Black Cat to Caxton Gibbet improvements

TR010044 Volume 7 7.10 Combined Modelling and Appraisal Report

Planning Act 2008 Regulation 5(2)(q) Infrastructure Planning (Applications: Prescribed Forms and Procedure) Regulations 2009

26 February 2021

A428 Black Cat to Caxton Gibbet improvements Combined Modelling and Appraisal Report

Infrastructure Planning

Planning Act 2008

The Infrastructure Planning (Applications: Prescribed Forms and Procedure) Regulations 2009

A428 Black Cat to Caxton Gibbet improvements Development Consent Order 202[ ]

Combined Modelling and Appraisal Report

Regulation Reference: Regulation 5(2)(q) Planning Inspectorate Scheme TR010044 Reference Application Document Reference TR010044/APP/) 7.10

Author A428 Black Cat to Caxton Gibbet Project Team, Highways England

Version Date Status of Version Rev 1 26 February 2021 DCO Application

Planning Inspectorate Scheme Ref: TR010044 Application Document Ref: TR010044/APP/7.10

A428 Black Cat to Caxton Gibbet improvements Combined Modelling and Appraisal Report

Table of contents

Chapter Pages Executive Summary 1 1 Introduction 5 1.1 Purpose 5 1.2 Background 6 1.3 Scheme description 8 1.4 Report structure 10 2 Local transport summary 11 2.1 Overview 11 2.2 Description of the local transport system 11 2.3 Description of traffic conditions in the Scheme area 13 2.4 Current transport issues 18 2.5 Data sources 20 2.6 ComMA data requirements 26 3 Model development 27 3.1 Introduction 27 3.2 Overview of the A428 strategic traffic model 27 3.3 The A428 strategic traffic model 28 3.4 Guidance applicable for development 31 3.5 A428 strategic traffic model development 32 3.6 Calibration and validation 37 3.7 Variable demand model 47 3.8 ComMA data requirements 48 4 Forecasting 50 4.1 Introduction 50 4.2 Assumptions 51 4.3 Forecast scenarios 54 4.4 Annual Average Daily Traffic (AADT) and other time period factors 56 4.5 Traffic forecasting outcomes 57 4.6 Operational models 82 4.7 ComMA Data Requirements 94 5 Economic appraisal 96 5.1 Economic appraisal approach 96 5.2 Scheme costs 102 5.3 Scheme benefits 104 5.4 Comparison of costs and benefits (including alternative growth scenarios) 116 5.5 ComMA data requirements 120

Planning Inspectorate Scheme Ref: TR010044 Application Document Ref: TR010044/APP/7.10

A428 Black Cat to Caxton Gibbet improvements Combined Modelling and Appraisal Report

6 Summary 122 6.1 The Scheme 122 6.2 Model development 122 6.3 Forecasts of future flows 123 6.4 Summary of economic appraisal 128 6.5 Consideration of results against scheme objectives 134 7 Glossary 135

Table of Figures Figure 1-1: Strategic Context ...... 6 Figure 1-2: Local Context ...... 7 Figure 1-3: The Scheme ...... 8 Figure 2-1: Road Network in the vicinity of the Scheme ...... 12 Figure 2-2: Average Annual Daily Flow...... 14 Figure 2-3: Daily Traffic Profile on A428 between Wyboston and Barford Road ...... 15 Figure 2-4: Daily Traffic Profile on A428 between Cambridge Road and Eltisley ...... 15 Figure 2-5: Observed Accident Locations (2011 – 2018) ...... 19 Figure 2-6: Depiction of Strategic Journey Time Routes for Model Validation ...... 24 Figure 2-7: Competing Journey Time Routes for Model Validation ...... 25 Figure 3-1: Regional Traffic Model (RTM) Suite Design ...... 29 Figure 3-2: A428 Strategic Traffic Model Network Coding Level of Detail ...... 30 Figure 3-3: Boundary of Area of Detailed Modelling ...... 32 Figure 3-4: Zone System for Area of Detailed Modelling (AoDM) ...... 33 Figure 3-5: A428 Strategic Traffic Model Survey Cordon and Screenlines ...... 34 Figure 3-6: SATURN ‘ME2’ Matrix Calibration Process ...... 39 Figure 3-7: A428 Strategic Traffic Model Cordon and Screenlines ...... 42 Figure 3-8: Demand Model Choice Hierarchy ...... 48 Figure 4-1: Uncertainty Log Study Area ...... 51 Figure 4-2: Sections of Existing and Proposed Route...... 59 Figure 4-3: Annual Average Daily Traffic (AADT), 2015 Base Year (Vehicles) ...... 65 Figure 4-4: Annual Average Daily Traffic (AADT), 2040 Do Minimum (Vehicles) ...... 66 Figure 4-5: Comparison of 2015 to 2040 DM - Percentage Change in AADT...... 67 Figure 4-6: Annual Average Daily Traffic (AADT), 2040 Do Something (Vehicles) ...... 68 Figure 4-7: Annual Average Daily Traffic (AADT), 2040 Do Something Less 2040 Do Minimum (Vehicles) ...... 69 Figure 4-8: Comparison of 2040 DM to 2040 DS - Percentage Change in AADT ...... 70 Figure 4-9: Journey Time Routes (Long Distance) ...... 71 Figure 4-10: Journey Time Routes (Local, Set 1) ...... 72 Figure 4-11: Journey Time Routes (Local, Set 2) ...... 72 Figure 4-12: Locations of the Local Modelled Junctions within the TA...... 83 Figure 4-13: Locations of the Wide Area Modelled Junctions in the TAA ...... 86 Figure 4-14: Summary of Impacts in Cambridgeshire ...... 89 Figure 4-15: Summary of Impacts in Bedford Borough ...... 92 Figure 4-16: Summary of Impacts in Central Bedfordshire ...... 94 Figure 5-1: Economics Sectors ...... 101 Figure 5-2: Profile of Benefits 2025 to 2084 (£000s Discounted and Deflated to 2010) .. 106

Planning Inspectorate Scheme Ref: TR010044 Application Document Ref: TR010044/APP/7.10

A428 Black Cat to Caxton Gibbet improvements Combined Modelling and Appraisal Report

Figure 5-3: Percentage of Total Journey Time / VOC benefits by Sector Origin ...... 109

Table of Tables Table 1-1: Client Scheme Requirements ...... 8 Table 2-1: Journey Time between Black Cat and Caxton Gibbet ...... 16 Table 2-2: Personal Injury Accidents by Severity and Year ...... 17 Table 2-3: Personal Injury Accidents by Route and Year...... 17 Table 2-4: Personal Injury Accidents Recorded as Serious in Severity by Scheme Area .. 17 Table 2-5: Observed Accidents and National Average Accidents ...... 19 Table 2-6: Sources of Existing Data and Use ...... 20 Table 2-7: Additional Survey Data for A428 Strategic Traffic Model ...... 21 Table 2-8: ComMA Data Requirements Summary – Chapter 2 ...... 26 Table 3-1: Model User Classes and Vehicle Classes ...... 31 Table 3-2: Values of Time and Vehicle Operating Costs ...... 36 Table 3-3: TAG Unit M3.1: Significance of Matrix Estimation Changes ...... 40 Table 3-4: Performance of Calibration Screenlines - Model Version ‘a’ ...... 42 Table 3-5: Performance of Validation Screenlines - Model Version ‘a’ ...... 42 Table 3-6: Performance of Calibration Screenlines - Model Version ‘b’ ...... 43 Table 3-7: Performance of Validation Screenlines - Model Version ‘b’ ...... 43 Table 3-8: TAG Link Flow and Turning Movement Calibration/Validation Criteria and Acceptability Guidelines ...... 44 Table 3-9: Total Calibration and Validation Counts (All Vehicles) – AM ...... 44 Table 3-10: Total Calibration and Validation Counts (All Vehicles) – IP ...... 45 Table 3-11: Total Calibration and Validation Counts (All Vehicles) – PM...... 45 Table 3-12: Highway Model Convergence Results ...... 47 Table 3-13: ComMA Data Requirements Summary – Chapter 3 ...... 49 Table 4-1: Summary of Forecast Scenarios ...... 56 Table 4-2: Light Vehicle Expansion Factors ...... 57 Table 4-3: Heavy Vehicle Expansion Factors ...... 57 Table 4-4: The Scheme by Identified Sections ...... 59 Table 4-5: AADT Vehicle Flows – Without-Scheme (Base Year 2015 and Forecast Years 2025, 2040 & 2051) ...... 60 Table 4-6: AADT Volumes Without and With-Scheme Scenarios (Forecast Years 2025, 2040 and 2051) ...... 61 Table 4-7: Comparison of Journey Time Changes (Long Distance Routes) ...... 74 Table 4-8: Comparison of Journey Time Changes (Local Routes) ...... 77 Table 4-9: Summary of Modelling Undertaken for Cambridgeshire Junctions ...... 87 Table 4-10: Summary of Junction Performance in Cambridgeshire ...... 88 Table 4-11: Summary of Modelling Undertaken for Bedford Borough Junctions ...... 90 Table 4-12: Summary of Junction Performance in Bedford Borough ...... 91 Table 4-13: Summary of Modelling Undertaken for Central Bedfordshire Junctions ...... 93 Table 4-14: Summary of Junction Performance in Central Bedfordshire ...... 93 Table 4-15: ComMA Data Requirements Summary – Chapter 4 ...... 95 Table 5-1: Annualisation Factors for AM, IP, PM and OP ...... 99 Table 5-2: Comparison of the Impacts of the Masking Tests on Present Value Benefits (PVBs) – All Time Periods ...... 102 Table 5-3: Operating and Maintenance Costs (2010 Undiscounted Factor Prices) ...... 103

Planning Inspectorate Scheme Ref: TR010044 Application Document Ref: TR010044/APP/7.10

A428 Black Cat to Caxton Gibbet improvements Combined Modelling and Appraisal Report

Table 5-4: Condensed Public Accounts Table (£000s Discounted and Deflated to 2010) ...... 104 Table 5-5: Transport Economic Efficiency Benefits (£000s Discounted and Deflated to 2010)...... 105 Table 5-6: TEE Benefits by Time Period (£000s Discounted and Deflated to 2010) ...... 106 Table 5-7: Benefits by User Class and Time Period (£000s Discounted and Deflated to 2010)...... 107 Table 5-8: Journey Time Benefits and Vehicle Operating Costs by Trip Time Variation (£000s Discounted and Deflated to 2010)...... 107 Table 5-9: Journey Time Benefits and Vehicle Operating Costs by Distance Travelled (£000s Discounted and Deflated to 2010)...... 108 Table 5-10: Accident Savings Over the 60-year Evaluation Period ...... 110 Table 5-11: Present Value of Accident Benefits (£000s Discounted and Deflated to 2010) ...... 110 Table 5-12: Summary of Environmental Impacts (£000s Discounted and Deflated to 2010) ...... 111 Table 5-13: Scheme Construction – Benefits by Construction Phase (£000s Discounted and Deflated to 2010) ...... 112 Table 5-14: Scheme Construction – Benefits by Road User (£000s Discounted and Deflated to 2010) ...... 112 Table 5-15: Relationships between Wider Economic Impacts, Level of Analysis and Land Use Assumptions ...... 113 Table 5-16: Results of WITA Analysis (£000s Discounted and Deflated to 2010) ...... 115 Table 5-17: Economic Appraisal Summary – Initial BCR ...... 116 Table 5-18: Aggregated AMCB Table (£000s Discounted and Deflated to 2010) ...... 118 Table 5-19: Adjusted BCR (£000s Discounted and Deflated to 2010) ...... 119 Table 5-20: Adjusted BCR by Growth Scenario ...... 119 Table 5-21: Carbon Cost Impacts on Core Growth Adjusted BCR ...... 120 Table 5-22: ComMA Data Requirements Summary – Chapter 5 ...... 121 Table 6-1: AADT Vehicle Flows (Two-Way) – Without-Scheme ...... 124 Table 6-2: AADT Vehicle Flows (Two-Way) – Without-Scheme – Core and Low Growth Scenarios ...... 124 Table 6-3: AADT Vehicle Flows (Two-Way) – With-Scheme ...... 126 Table 6-4: Comparison of Journey Time Changes in 2040 (Longer Routes) ...... 127 Table 6-5: BCR and Adjusted BCR for Core, Low & High Growth Scenarios (£000s Discounted and Deflated to 2010) ...... 128 Table 6-6: Key Monetised Benefits and Costs ...... 131 Table 6-7: Key Quantified Benefits and Disbenefits ...... 132 Table 6-8: Summary of Objectives and Outcomes...... 134

Planning Inspectorate Scheme Ref: TR010044 Application Document Ref: TR010044/APP/7.10

A428 Black Cat to Caxton Gibbet improvements Combined Modelling and Appraisal Report

Appendices Appendix A Transport Data Package: Traffic Data Collection Report (TDCR) Appendix B Transport Model Package: Local Model Validation Report (LMVR) Appendix C Transport Forecasting Package: Traffic Forecasting Report (TFR) Appendix D Economic Appraisal Package: Economic Assessment Report (EAR) Appendix E Economic Appraisal Package: Appraisal Summary Table (AST) and Supporting Worksheets Report Appendix F Economic Appraisal Package: Distributional Impacts Report (DIR)

Planning Inspectorate Scheme Ref: TR010044 Application Document Ref: TR010044/APP/7.10

A428 Black Cat to Caxton Gibbet improvements Combined Modelling and Appraisal Report

Executive Summary

This Combined Modelling and Appraisal (ComMA) Report details the modelling and appraisal work undertaken for the A428 Black Cat to Caxton Gibbet improvements (the Scheme). The Scheme is a 10-mile dual carriageway from west of the A421/A1 Black Cat roundabout through to east of the A428/A1198 Caxton Gibbet roundabout with grade separated junctions at Black Cat, Cambridge Road and Caxton Gibbet. The ComMA report is an ‘end of stage’ document that describes the model development, forecasting and economic appraisal carried out for the Scheme. Travel demand and network performance of the A428 between the Black Cat junction and Caxton Gibbet and within the road network local to the Scheme have specific characteristics. These include: a. Congestion – junctions are currently operating close to or at capacity and links are coping with traffic volumes that are double the capacity that they were designed for. b. Traffic speed – average peak speed can be as low as one third of average free flow speed. c. Delays – journeys can take up to 65% longer during peak hours. d. Reliability – congestion, low traffic speeds and delays mean that journey times are unreliable, impacting on productivity. e. Resilience – there is low resilience to incidents on the single carriageway section of the A428. The A428 Strategic Traffic Model, used to support the Development Consent Order (DCO) application, is a new traffic model developed from Highways England’s South East Regional Traffic Model (SERTM). The A428 Strategic Traffic Model was developed to expand on the area that the previous traffic model covered, which was used in earlier Project Control Framework (PCF) Stages, and it utilised more recent and robust traffic demand data. The primary use of the A428 Strategic Traffic Model is to assess the traffic impacts of the A428 Black Cat to Caxton Gibbet Improvements scheme and to provide inputs into economic and environmental appraisals, as well as informing the buildability (construction traffic management) of the Scheme and operation and design of its junctions. The A428 Strategic Traffic Model is a strategic model which extends across England and Wales with an ‘Area of Detailed Modelling (AoDM)’ covering Cambridge, Huntingdon, St Neots, and Bedford.

Planning Inspectorate Scheme Ref: TR010044 1 Application Document Ref: TR010044/APP/7.10

A428 Black Cat to Caxton Gibbet improvements Combined Modelling and Appraisal Report

The base year for the model is 20151, calibrated to represent a June 2015 weekday2. Separate models were developed to reflect an average peak hour across a morning, interpeak and evening peak period. All the models were calibrated and validated to a standard which meets or exceeds Department for Transport (DfT) thresholds. In addition to the strategic modelling, a number of operational models were developed to facilitate a detailed assessment of junction capacities and layouts. VISSIM microsimulation modelling has been undertaken for the three main junctions of the Scheme at Black Cat (A1/A421-A428); Cambridge Road (A428/B1428) and Caxton Gibbet (A428/A1198). A number of other models were developed using TRL Junctions 9 software ARCADY3 and PICADY4 to assess existing junctions that are either modified as part of the Scheme proposals, are in close proximity to the Scheme, or are affected due to flow changes as a result of the Scheme. Future year models were developed from the base year by considering planned local land use and transport infrastructure changes alongside national projections of population and economic changes. Future year models were built for 2025 – the year the Scheme is assumed to be open to traffic, 2040 and 2051. However, since the traffic forecasts were prepared, Highways England has defined a reasonable worst case scenario construction programme, which assumes the ‘advanced works’ and the ‘enabling works’ being undertaken post grant of the A428 Order. This may result in a 2026 opening year. This difference between the opening years does not invalidate the conclusions of the either the Traffic or Economic Assessment of the Scheme as presented in this report. The forecast flows on the road network in years 2025 and 2040 are considered to be reasonably representative of the traffic flows that would exist on the network in year 2026 and 2041 respectively. A set of models without the Scheme, referred to as Do Minimum (DM) models, were built to represent how the network would operate without the Scheme. The Do Something (DS) models demonstrate the operational impact with the Scheme. Differences between the model predictions of flows, journey times and travelled distances are obtained from the models and are monetised in the economic appraisal. Flows from both the DM and DS models also formed the basis for environmental appraisals and safety assessments. A series of sensitivity tests were undertaken to consider how sensitive the flows, journey times and travelled distances are to changes in some of the key assumptions. This scenario testing is required by the DfT to demonstrate the robustness of the core results which are being relied on as the main evidence.

1 The model base year was defined as 2015 which reflects the age of the mobile phone demand data in the SERTM. 2 As the Black Cat ‘Pinch Point’ improvement scheme opened on 27 March 2015 resulting in some significant increases in traffic over the following few months, the model has been calibrated and validated to an equivalent June 2015 weekday. 3 https://trlsoftware.com/products/junction-signal-design/junctions/arcady/ 4 https://trlsoftware.com/products/junction-signal-design/junctions/picady/

Planning Inspectorate Scheme Ref: TR010044 2 Application Document Ref: TR010044/APP/7.10

A428 Black Cat to Caxton Gibbet improvements Combined Modelling and Appraisal Report

The models demonstrated that the Scheme would provide a reduction in journey times in each modelled period. The largest impact produced a travel time with the Scheme which is 14 minutes less than the without Scheme scenario in 2040. In addition to the reduced journey times, the traffic modelling demonstrated that the Scheme would provide significant relief to the existing A428 between Cambridge Road junction and Caxton Gibbet, with reductions in traffic volumes of around 95%. The economic appraisal used outputs from the future year models and applied a monetary value to the time saved and a cost to the fuel consumed. The process subtracts the travel costs in the Do-Something from those of the Do-Minimum to derive the economic benefits for the Scheme. These are discounted in each of the 60 years of the appraisal period and summed for comparison against the costs of the Scheme, including any costs or values associated with mitigating adverse impacts, to create the initial benefit to cost ratio. Changes in the number of accidents, air quality, noise and greenhouse gases have been assessed, together with an assessment of impacts during construction. These have been monetised and are included in the economic appraisal. In addition to the initial estimate of benefits, journey time reliability and wider economic impacts have been determined to adjust the benefit to cost ratio. These wider impacts are an assessment of how the economy reacts to the Scheme primarily through business agglomeration but also employees having access to employment and better paying jobs. The overall economic appraisal of the Scheme shows it has beneficial impacts on all journey purposes in all modelled periods and a beneficial impact on the wider economy. The Present Value of Benefits (PVB) (excluding journey time reliability and wider economic impacts) amounts to £541 million. When compared to the estimated cost to the public sector of £463 million this produces an initial Benefit to Cost Ratio (BCR) of 1.2. With journey time reliability and wider economic impacts included, the PVB increases to £883 million producing an adjusted BCR of 1.9. In July 2020 the Department for Transport published ‘A route map for updating Transport Analysis Guidance (TAG) during uncertain times’. This was a response to the unexpected events which have occurred including the COVID-19 virus and the changes to the economic and fiscal outlook that have the potential to have a significant bearing on scheme appraisals. The route map sets out how the appraisal framework should take account of these future trends in relation to the methods used within TAG. It is expected that revised TAG guidance will be issued in Spring 2021 with subsequent updates issued as and when issues are addressed. The route map advises that the impact of the new Office for Budget Responsibility (OBR) economic growth forecasts and high carbon values should be undertaken through the use of sensitivity testing prior to the release of formal changes to TAG guidance in 2021. It should be noted that the traffic forecasts and economic appraisal for the Scheme were completed prior to the publication of the DfT route map. However, it is intended that the impacts of uncertainty will be informed by the route map through sensitivity testing.

Planning Inspectorate Scheme Ref: TR010044 3 Application Document Ref: TR010044/APP/7.10

A428 Black Cat to Caxton Gibbet improvements Combined Modelling and Appraisal Report

A sensitivity test using the interim carbon values has been undertaken. The High Carbon Sensitivity was shown to reduce the adjusted BCR from 1.9 to 1.8. The results are presented in section 5.4 of this report. Given the more complex processes involved, it has not been possible to complete a sensitivity test to assess the impact of the latest projections of economic growth in advance of submission of the DCO application. Therefore, a sensitivity test on economic growth will be prepared in accordance with relevant DfT guidance as soon as practically possible following acceptance of the DCO application. Our approach to dealing with the uncertainty arising from COVID-19 and the resultant changes to the economic outlook is described in more detail in ‘Strategy for Dealing with Uncertain Outcomes Arising from COVID-19’ [TR010044/APP/7.11] and in section 5.1 of this report.

Planning Inspectorate Scheme Ref: TR010044 4 Application Document Ref: TR010044/APP/7.10

A428 Black Cat to Caxton Gibbet improvements Combined Modelling and Appraisal Report

1 Introduction

1.1 Purpose The A428 Black Cat to Caxton Gibbet improvements (the Scheme) is being developed by Highways England (the Applicant) as part of its responsibility to deliver the Road Investment Strategy (RIS) and to operate, maintain and modernise the Strategic Road Network (SRN)5. The Scheme is designed to dual the last remaining single carriageway section of the SRN between M1 J13 (South East of Milton Keynes) and the Port of Felixstowe, via Cambridge and the A14. The purpose of this Combined Modelling and Appraisal (ComMA) Report is to summarise the work undertaken to model and appraise the impact of the Scheme on the strategic and local highway network, road safety and the economy. It is submitted as part of the Development Consent Order (DCO) application. The ComMA links to, and summarises, the following packages detailing the technical transport modelling and appraisal work undertaken as part of this project and which are standalone Appendices to this document: a. The Transport Data Package: Traffic Data Collection Report (TDCR)6, Appendix A to the ComMA. b. The Transport Model Package: Local Model Validation Report (LMVR)7, Appendix B to the ComMA. c. The Transport Forecasting Package: Traffic Forecasting Report (TFR)8, Appendix C to the ComMA. d. The Economic Appraisal Package, which includes the following reports: i. Economic Assessment Report (EAR)9, Appendix D to the ComMA. ii. Distributional Impacts Report (DIR)10, Appendix E to the ComMA. iii. Appraisal Summary Table (AST) and Supporting Worksheets Report11, Appendix F to the ComMA.

5 The SRN in England is made up of motorways and trunk roads, the most significant ‘A’ roads. It represents around two per cent of all roads in England by length, but it carries a third of all traffic by mileage, and two thirds of all heavy goods vehicle traffic. 6 Traffic Data Collection Report (TDCR) - HE551495-ACM-GEN-GEN_SW_Z_ZZ-RP-TR-0002 7 Local Model Validation Report (LMVR) - HE551495-ACM-GEN-GEN_SW_Z_ZZ-RP-TR-0005 8 Traffic Forecasting Report (TFR) - HE551495-ACM-GEN-GEN_SW_Z_ZZ-RP-TR-0008 9 Economic Assessment Report (EAR) - HE551495-ACM-GEN-GEN_SW_Z_ZZ-RP-TR-0009 10 Distributional Impacts Report (DIR) - HE551495-ACM-GEN-GEN_SW_Z_ZZ-RP-TR-0006 11 Appraisal Summary Table (AST) and Supporting Worksheets Report - HE551495-ACM-GEN- GEN_SW_Z_ZZ-RP-TR-0011

Planning Inspectorate Scheme Ref: TR010044 5 Application Document Ref: TR010044/APP/7.10

A428 Black Cat to Caxton Gibbet improvements Combined Modelling and Appraisal Report

The ComMA is intended to summarise the programme of data collection undertaken at the onset of this Project Control Framework (PCF) Stage 3 appraisal; the development of the Base Year (BY) and Forecast Year (FY) transport models; and to present the findings of the economic appraisal of the Scheme.

1.2 Background The A428 between Wyboston and Caxton Gibbet is the only section of single carriageway of the 108 miles of SRN between M1 J13 and the Port of Felixstowe via Cambridge and the A14, and it is 10 miles of length. It is also at the eastern end of the Oxford to Cambridge (Ox-Cam) arc of innovation and entrepreneurial growth (Figure 1-1 and Figure 1-2 below). The A428 enables people to travel to work, make business trips and travel for tourism and other leisure purposes. The road is also on the important freight transport route between the Haven ports and the Midlands (HGV)12.

12 Felixstowe to the Midlands Route Strategy Evidence Report, Highways Agency (2014)

Planning Inspectorate Scheme Ref: TR010044 6 Application Document Ref: TR010044/APP/7.10

A428 Black Cat to Caxton Gibbet improvements Combined Modelling and Appraisal Report

Problems on this section of the road are identified in the A428 Route Strategies Options Appraisal Report (OAR)13 and Traffic Forecasting Report. Junctions along the existing A428 are operating at or close to capacity, with high levels of congestion and unreliable journey times. The current problems on the route are detailed in section 2.3 of this report. The Department for Transport (DfT) forecasts for the SRN show an increase of between 29% (low growth) and 59% (high growth) by 2050, from 201514. This growth will exacerbate existing problems resulting in ambitious development proposals for housing and employment, both locally and in the wider area, being constrained. Objectives for the Scheme have been formulated both to address identified problems and to take advantage of the opportunities that the new infrastructure will provide. The objectives are defined in the DfT’s Client Scheme Requirements (CSRs) which respond directly to the need for change and are presented in Table 1-1.

13 https://highwaysengland.citizenspace.com/he/a428-black-cat-to-caxton- gibbet/supporting_documents/A428%20Options%20Assessment%20Report.pdf 14 Road Traffic Forecasts 2018, paragraph 15

Planning Inspectorate Scheme Ref: TR010044 7 Application Document Ref: TR010044/APP/7.10

A428 Black Cat to Caxton Gibbet improvements Combined Modelling and Appraisal Report

Table 1-1: Client Scheme Requirements

To support significant levels of planned economic growth in Cambridge Economic and the surrounding sub-region, which is one of the fastest growing growth areas of the UK.

To reduce traffic congestion, provide adequate capacity to support Transport future growth forecasts, improve journey time reliability and increase resilience against accidents and incidents.

To protect the built and natural environment by mitigating the Environment potentially adverse impact of adding additional capacity where technically feasible and economic to do so.

To enhance accessibility and reduce severance for non-motorised Community road users where technically feasible and economic to do so.

1.3 Scheme description The purpose of the Scheme is to address the problems of congestion, poor journey time reliability and poor resilience against incidents between the Black Cat and Caxton Gibbet roundabouts. The Scheme seeks to address these problems through construction of a new 10 mile (16km) dual 2-lane carriageway from the Black Cat roundabout to Caxton Gibbet roundabout, to be known as the A421 (hereafter referred to as the ‘new dual carriageway’), and in addition approximately 1.8 miles (3km) of tie-in works shown in schematic form in Figure 1-3 below.

Figure 1-3: The Scheme

Planning Inspectorate Scheme Ref: TR010044 8 Application Document Ref: TR010044/APP/7.10

A428 Black Cat to Caxton Gibbet improvements Combined Modelling and Appraisal Report

The Scheme includes the following components: a. A new three-level grade separated junction at Black Cat roundabout, with the A1 at the lower level, the new dual carriageway on the upper level and a roundabout between the two at approximately existing ground level. In addition to slip roads a new free flowing link between the A421 eastbound carriageway and the A1 northbound carriageway will also be provided. b. A new grade separated all movements junction will be constructed to the east of the existing Cambridge Road roundabout to provide access to the new dual carriageway and maintain access to the existing A428. c. At the Caxton Gibbet roundabout, a new grade separated all movements junction will be constructed, incorporating the existing roundabout on the south side of the new dual carriageway and a new roundabout on the north side. The new dual carriageway will then tie-in to the existing A428 dual carriageway to the east of the new Caxton Gibbet junction. d. In the vicinity of the new Black Cat junction, direct access onto the A1 from some local side roads and private premises will be closed for safety reasons. A new local road will provide an alternative route. The existing Roxton Road bridge will be demolished and replaced with a new structure to the west to accommodate the realigned A421. e. New crossings will be constructed to enable the new dual carriageway to cross the River Great Ouse, East Coast Main Line railway, Barford Road, the B1046/Potton Road, Toseland Road and the existing A428 at Eltisley. f. The existing A428 between St Neots and Caxton Gibbet will be de-trunked and retained for local traffic and public transport with maintenance responsibility transferred to the local highway authorities. g. An alternative access will be provided to side roads at Chawston, Wyboston and Eltisley. h. There will be safer routes for walkers, cyclists and horse riders. The objectives of the Scheme are as follows: a. Connectivity: Cut congestion and increase capacity and journey time reliability between Milton Keynes and Cambridge. b. Safety: Improve safety at junctions, side roads and private accesses by reducing traffic flows on the existing A428. Improve safety on the A1 by removing existing substandard side road junctions and private accesses onto the carriageway. c. Economic growth: Enable growth by improving connections between people and jobs and supporting new development projects. d. Environmental improvements: Maintain existing levels of biodiversity and have a beneficial impact on air quality and noise levels in the surrounding area.

Planning Inspectorate Scheme Ref: TR010044 9 Application Document Ref: TR010044/APP/7.10

A428 Black Cat to Caxton Gibbet improvements Combined Modelling and Appraisal Report

e. Accessibility: Ensure the safety of cyclists, walkers, horse riders and those who use public transport by improving the routes and connections between communities. f. Resilience: Improve the reliability of the road network so that it can cope better when accidents occur, without local roads being used as diversion routes. g. Customer Satisfaction: Listen to what is important to our customers to deliver a better road for everyone and improve customer satisfaction.

1.4 Report structure The ComMA report is an ‘end of stage’ document encapsulating the majority of reporting on the model development, forecasting and appraisal undertaken for the Scheme. This ComMA details the modelling and appraisal work undertaken for the A428 Black Cat to Caxton Gibbet Improvements scheme. Following this introductory chapter, the remainder of the ComMA is structured as follows: a. Chapter 2: Local Transport Summary. b. Chapter 3: Model Development. c. Chapter 4: Forecasting. d. Chapter 5: Economic Appraisal. e. Chapter 6: Summary. A glossary of abbreviations can be found at the end of this document.

Planning Inspectorate Scheme Ref: TR010044 10 Application Document Ref: TR010044/APP/7.10

A428 Black Cat to Caxton Gibbet improvements Combined Modelling and Appraisal Report

2 Local transport summary

2.1 Overview Travel demand and network performance in the vicinity of the Scheme have particular characteristics, which influence transport modelling and scheme appraisal. For example: a. Congestion – junctions are currently operating close to or at capacity and links are coping with traffic volumes that are double the capacity that they were designed for. Forecasted growth between 2015 and 2051 shows an increase by 18% for Heavy Goods Vehicles (HGV), 50% for Light Goods Vehicles (LGV) and car traffic growth of 34%; b. Traffic speed – average peak speed can be as low as one third of average free flow speed; c. Delays – journeys can take up to 65% longer during peak hours; d. Reliability – congestion, low traffic speeds and delays mean that journey times are unreliable, impacting on productivity; and e. Resilience – there is low resilience to incidents on the single carriageway section of the A428. This section describes the baseline conditions making use of traffic data collected for PCF Stage 2 of the model and new data specifically collected to support the development of the traffic model for PCF Stage 3.

2.2 Description of the local transport system Highway network The A428 forms a key section of the strategic east / west corridor between the A43 / M40 near Bicester, the M1 near Bedford / Milton Keynes, the A1 / A428 near St Neots, and the A14 / M11 / A428 near Cambridge. It links Oxford to Cambridge and the Haven Ports of Felixstowe, Harwich and Ipswich, via Milton Keynes and Bedford. The A428 extends approximately 17 miles between the A1 and A14 / M11 west of Cambridge. It is a single carriageway for 8.5 miles between the A1 at St. Neots to the A1198 at Caxton Gibbet with a range of at grade-junctions and direct accesses to private properties. This corridor provides an alternative route choice for east-west movements between the Midlands to the Haven Ports using the A14. The road network in the vicinity of the Scheme is illustrated in Figure 2-1 below.

Planning Inspectorate Scheme Ref: TR010044 11 Application Document Ref: TR010044/APP/7.10

A428 Black Cat to Caxton Gibbet improvements Combined Modelling and Appraisal Report

Figure 2-1: Road Network in the vicinity of the Scheme

Local and strategic public transport options The A428 corridor is not currently served by rail although there are proposals for an East-West rail connection between Bedford and Cambridge as noted in paragraph 2.2.11 below. There are limited bus and coach options available. Of the bus services along the A428, the X5 service operated by Stagecoach runs between Cambridge and Oxford via St Neots, Bedford and Milton Keynes. It operates every 30 minutes for most of the day, and up to every 15 minutes during the morning and evening peaks and takes up to 4 hours to complete the journey. The car journey time from Cambridge to Oxford with no delays is of the order of two hours. Two National Express coach services also operate along the A428 at a frequency of once per day: the 305 service between Liverpool and Clacton-on-Sea and the 314 service between Southport and Cambridge. Both services stop at Bedford, St Neots, Cambourne and Cambridge. Improving journey reliability would enable operators to run more reliable services, thereby improving connectivity to link people with jobs. There are no local bus services connecting Cambridge and St Neots, despite the close economic ties between the two, with a strong commuter flow from St Neots to Cambridge. However, there is a Stagecoach bus service which connects Cambridge with Cambourne and the intermediate villages, making use of the previous A428 road which was replaced by the A428 Caxton Common to Hardwick scheme in 200715.

15 http://news.bbc.co.uk/1/hi/england/cambridgeshire/6688331.stm

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The Greater Cambridge Partnership also has proposals to provide a busway between Cambourne and Cambridge (C2C) as the first phase of the Cambridgeshire and Peterborough Combined Authority’s plans for the Cambridgeshire Autonomous Metro (CAM). St Neots Railway Station is located on the East Coast Main Line (ECML) and provides rail services to London every 10-20 minutes in the peak and every 30 minutes off-peak. Journey times are between 45 and 71 minutes to London. Services to Peterborough are half hourly in both peak and off-peak and typically take around 25 minutes. As noted above, no east-west rail services currently operate in the study area, however, East West Rail (EWR) consulted on five route options from January to March 2019. A preferred route announcement was made in January 2020, selecting the northern route, linking Bedford and Cambridge via south St Neots and Cambourne. A non-statutory public consultation is planned for early 2021 that will be followed by an announcement on the route alignment later in the year.

2.3 Description of traffic conditions in the Scheme area Observed traffic flows Figure 2-2 summarises traffic flows (Highways England’s WebTRIS16 data, 2018) on the A428 and on the road network in the vicinity of the Scheme.

16 A web-based platform to provide traffic flow data held by Highways England http://webtris.highwaysengland.co.uk/

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This shows more than 11,000 vehicles per day in both directions along the single carriageway sections of the A428 between Wyboston and Caxton Gibbet, and more than 30,000 vehicles per day between the A1 Black Cat Roundabout and its junction with the A428 at St Neots as east-west traffic interacts with north- south traffic on the A1. Daily flow profile Figure 2-3 and Figure 2-4 show the daily profile of 2-way hourly combined traffic (eastbound and westbound directions) on the A428 between Wyboston and Barford Road (site 128), and between Cambridge Road and Eltisley (site 131) respectively. These are based on an Automatic Traffic Count (ATC) survey undertaken in 2016 for the A428 Stage 2 model. The morning peak demand (2577 vehicles/hour) occurs in mid-week between 08:00 and 09:00 at site 128, and the afternoon peak occurs mid-week (2806 vehicles/hour) between 17:00 and 18:00. There is a clear distinction between Monday-Friday commuter peaks and the weekend profile, with the weekend morning peak occurring around 11:00 to 12:00. The daily flow profile of site 131 is similar to site 128. However, the morning peak demand (1924 vehicles/hour) occurs between 07:00 and 08:00, and the traffic on the A428 between Cambridge Road and Eltisley is generally less (approximate 600 vehicles/hour) than the section between Wyboston and Barford Road.

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Site 128 1400 Mon

1200 Tue

Wed 1000 Thu 800 Fri 600

Sat Vehicles / / Hour Vehicles 400 Sun

200 W'Da y Av

0 7 Day

09:00 18:00 03:00 06:00 12:00 15:00 21:00 00:00 Av

Hour Starting Figure 2-3: Daily Traffic Profile on A428 between Wyboston and Barford Road

Site 131

Mon 1400

Tue 1200 Wed 1000 Thu

800 Fri

600 Sat

Vehicles / / Hour Vehicles Sun 400

W'Da 200 y Av

7 Day Av

00:00 03:00 06:00 09:00 12:00 15:00 18:00 21:00

Hout Starting Figure 2-4: Daily Traffic Profile on A428 between Cambridge Road and Eltisley

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Journey times Trafficmaster (TM) data obtained from the DfT was used to provide average journey times. TM data is obtained from various types of vehicles including fleet vehicles, LGVs, HGVs and buses, using in-vehicle Global Positioning Systems (GPS) devices and trackers. It takes the form of average observed journey times by Ordnance Survey (OS) MasterMap Integrated Transport Network (ITN) links, which can be added together to define the required route times in total and by way point and both by time period. Table 2-1 provides the average journey time between Black Cat junction and Caxton Gibbet junction by time period, based on the data available for June 2015.

Table 2-1: Journey Time between Black Cat and Caxton Gibbet

Time Period Direction Journey Time (mm:ss)

EB 17:51 AM (07:00 - 10:00) WB 16:52

EB 14:13 IP (10:00 - 16:00) WB 14:11

EB 15:28 PM (16:00 - 19:00) WB 15:11

Personal injury accidents A high-level accident review was undertaken using Personal Injury Accidents (PIAs) data for the five-year period between 2011 and 2015. The extent of the PIA study area includes the existing A1 from the Barford Road junction in the south, to the slip roads of the Wyboston junction to the north, and the existing A421 from Roxton Road overbridge to the Black Cat roundabout. From the slip roads at Wyboston, the existing A428 has been included as far as the eastern approach to the existing Caxton Gibbet roundabout. A summary of PIAs and casualties are presented in Table 2-2.

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Table 2-2: Personal Injury Accidents by Severity and Year

Severity Year Total Fatal Serious Slight

2011 0 4 28 32

2012 2 3 31 36

2013 0 6 29 35

2014 0 7 28 35

2015 0 4 19 23

Total 2 24 135 161

A summary of the accidents broken down by route is provided in Table 2-3.

Table 2-3: Personal Injury Accidents by Route and Year

Year Scheme Area Total 2011 2012 2013 2014 2015

A1 14 6 14 9 8 51

A421 2 1 4 3 0 10

A428 16 29 17 23 15 100

Total 32 36 35 35 23 161

The number of serious accidents that occurred in the three main aspects of the study area are set out in Table 2-4. A total of 24 serious accidents were recorded within the study area during the study period.

Table 2-4: Personal Injury Accidents Recorded as Serious in Severity by Scheme Area

Accidents Recorded as Serious in Location Severity

A1 5

A421 3

A428 16

Total 24

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2.4 Current transport issues The A428 between Wyboston and Caxton Gibbet is the only section of the SRN that is a single carriageway between M1 J13 and the Port of Felixstowe via Cambridge and the A14. The A428 experiences significant junction capacity issues; specifically, the Felixstowe to Midlands Route Strategy17 highlighted the following: a. Severe lack of capacity (links and junctions) on the A428 between the A1 and A1198. b. Congestion and delays. c. Low traffic speed and unreliable journey times. d. A lack of resilience to incidents on the single carriageway section of the A428 between the A1 / A421 Black Cat Roundabout and A428 / A1198 Caxton Gibbet Roundabout. Motorists experience regular delays and congestion as the A1 and A428 pass through rural communities and villages, and particularly at the A1 / A421 Black Cat and A428 / A1198 Caxton Gibbet roundabouts. The A428 Route Strategies Options Appraisal Report (OAR) identified the problems faced by the A428: a. It carries twice the traffic it was designed for. b. The route, as a whole, was identified as having safety and maintenance issues. c. The A428 between Wyboston and Caxton Gibbet was identified as having peak hour speeds of less than 40mph with link delays in the top 20% nationally. d. Journey times on the A428 were identified as being some of the least reliable nationally. e. Black Cat roundabout was identified as having a safety problem (69th highest number of accidents nationally). f. The A428 between Wyboston and Caxton Gibbet was identified as being within the top 25% of highway links nationally for casualties per billion vehicle miles.

17https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/600309/ Felixstowe_to_Midlands_Final.pdf

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Accident data Table 2-5 presents the number of observed accidents within the A421 / A428 corridor between 2011 and 2015. The 5-year observed average is higher than the national accident rate calculated for 2015. It should be noted that the Black Cat roundabout was signalised in 2015 as part of Highway England’s Pinch Point Programme (PPP). Therefore, a like-for-like comparison of accidents is only possible for the years leading up to 2015.

Table 2-5: Observed Accidents and National Average Accidents

5-year Year 2011 2012 2013 2014 2015 Average

Number of accidents calculated to - - - - 32 - national rates*

Number of observed accidents 34 40 34 40 28 35

* The calculation is based on AADT data which is only available for the base year 2015. Figure 2-5 shows the location of the accidents listed in the Table (2011 to 2015), along with data between 2016 and 2018. Additionally, there is a significant clustering of accidents around Black Cat junction and Caxton Gibbet junction.

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2.5 Data sources Stage 2 model data Existing data sources used for the development of the Stage 2 model that were available and used in the A428 Strategic Traffic Model are summarised in Table 2-6. The data sources are described in more detail in Chapter 3 of the Traffic Data Collection Report (TDCR), which is included as Appendix A of this report. The primary sources of data used to develop the A428 Strategic Traffic Model are described in Table 2-6 and comprised: a. ATC - Automatic Traffic Counts. b. MCLC – Manual Classified Link Counts. c. MCTC – Manual Classified Turning Counts. d. RSI – Roadside Interviews. e. JT – Journey Times.

Table 2-6: Sources of Existing Data and Use

Item Available Primary Use - Summary Data Source Year Primary Use No Data ATC MCLC MCTC RSI JT

To calibrate / validate the Stage 2 Traffic model and to 1 2016    Model counts. code model network including signal timings.

2015 To calibrate / Traffic 2 WebTRIS 2016 validate the  count data 2017 model.

To calibrate / 2015 validate the Journey 3 Trafficmaster 2016 model and to  time data 2017 assess ‘Reliability’.

To help develop St Neots 4 RSI data 2009 demand  Traffic Model matrices.

For the Stage 2 model, a significant number of Automatic Traffic Counts (ATCs) were undertaken in April/May 2016 for the calibration and validation of that model. Each site monitored traffic flows in both directions and categorised vehicle types and vehicle speeds. A limited number of Manual Classified Link Counts (MCLCs) and Manual Classified Turning Counts (MCTCs) were also available from the Stage 2 Model. Where appropriate, this data was used for validation / calibration.

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Data from a number of WebTRIS sites was also used to calculate suitable adjustment factors to enable the conversion of survey data to the common base of June 2015. This was done on the basis of road sections so that more local variation could be taken into account in the factors derived. A summary of the model input data by time period is provided in Appendix B of the Stage 3 Traffic Data Collection Report. Data for A428 strategic traffic model The A428 Strategic Traffic Model required additional surveys to supplement the existing data, particularly where there were gaps in the screenlines and cordons and where more information was needed on vehicle classification and turning movements. Survey programme The additional traffic survey and data collection tasks were commissioned by AECOM on behalf of Highways England. The majority were conducted by Intelligent Data Collection (IDC) Limited. The Automatic Number Plate Recognition (ANPR) surveys and a small number of additional counts were conducted by TRACSIS. The surveys are detailed in Table 2-7. The paragraph and table numbers in the table reference the Stage 3 Transport Data Package: Traffic Data Collection Report included in Appendix A.

Table 2-7: Additional Survey Data for A428 Strategic Traffic Model

Item Date of Reported in the following Type of survey no. surveys Sections of the TDCR

Automatic Traffic Counts (ATCs) 27/06/2017 Paragraph 5.1.3, 1 This data was used to check the seasonal variability and for model calibration and to 24/11/17 Table 5-1: ATC Locations validation of the model.

Observed Link Count Surveys 12/09/17 to Paragraph 5.2.2, Same purpose as ATCs. Where ATC 27/09/17, 2 counters cannot be placed due to safety 16/04/18 to Table 5-2: Video Link Count reasons video counts were conducted to 29/04/18 Locations obtain the data.

Manual Classified Counts (MCCs) – The 12 13/07/2017 hour MCC surveys were conducted to check to 16/11/17, Paragraph 6.1.5 3 the validity of flows at ATC sites and to 20/03/18 to Table 6-1: MCC Locations provide vehicle classification data 27/03/18

Manual Classified Turning Counts (MCTCs) 12/09/2017 Paragraph 6.2.2 4 This data was used for junction analysis and to Table 6-3: Location of MCTC to calculate proportion of different type of 16/11/2017 Sites vehicles

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Item Date of Reported in the following Type of survey no. surveys Sections of the TDCR

Automatic Number Plate Recognition (ANPR) This survey was conducted to check key Paragraph 7.1.2 5 movements at junctions, for developing 18/10/2017 Table 7-1: List of ANPR Sites strategic and microsimulation models and to identify possible routes for routing through ‘rat-runs’,

Weaving survey was undertaken on A1 to 6 the north of Black Cat Roundabout to 26/09/2017 Paragraph 8.1.1 understand levels of weaving and lane usage

Minor Access survey – Minor access Paragraph 8.1.1 surveys were conducted to provide 26/07/18 & 7 information for design purposes and impacts 28/07/18 Table 8-1: List of Sites for on safety Video

19/03/18 to Paragraph 5.1.3, 8 Additional ATCs – Same purpose as item 1 05/04/18 Table 5-1: ATC Locations

Additional ATCs September Paragraph 5.3.1 9 To identify seasonal variation 2017 Table 5 3: Resurveyed Sites

Paragraph 6.1.6 Additional MCCs – Purpose same as item 2. 26/06/18 to 10 These surveys were conducted for locations Table 6-2: Location of 27/06/18 where ATC surveys are not feasible. Additional Manual Classified Counts

Survey dates The equipment requirements for undertaking this number of surveys was significant and it was not possible to gain all permissions required from the Local Highway Authority. Surveys were therefore staggered before and after the summer holiday period and certain sites repeated and paired to check for any seasonal variation. Although July is not defined as a neutral month for the purpose of data collection a review of traffic conditions on the A428 showed that conditions in the early to mid-part of July were not significantly different to June or other neutral months. Surveys were therefore staggered before and after the holiday period, and certain sites repeated and paired to check for any seasonal variation (described in paragraph 2.5.13). Origin-Destination (OD) data Sources of OD data that have been used in the model development for PCF Stage 3 include:

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a. Trafficmaster-based (collected via GPS) matrix data for LGV movements, and DfT Base Year Freight Model (BYFM)-based matrix data for HGV movements, from Highways England’s South East Regional Traffic Model (SERTM) (item 3 of Table 2-2 above); b. An Automatic Number Plate Recognition (ANPR) survey (item 5 of Table 2-7) was undertaken to enable checks on key movements at junctions; the identification of possible east / west rat-running movements that were being used in preference to the main A428 / A421 route; and more generally, for both strategic and operational (microsimulation) modelling. c. Roadside Interview (RSI) data, (item 4 of Table 2-6), collected in 2009 was available for a cordon around St Neots to refine prior matrix demand data in this area. Traffic count data Automatic Traffic Counts (ATCs) were undertaken (item 1 of Table 2-7) for two weeks. Repeat surveys were also undertaken at 10 sites (item 9 of Table 2-7) in September 2017 to check for seasonal variability in the counts and provide reassurance that the July data could be used in developing the Base Year traffic model. Where sites were considered unsafe for the placing of pneumatic tubes to undertake ATCs, surveys (item 2 of Table 2-7) were undertaken using cameras. Manual classified link counts (MCLCs, item 3 of Table 2-7) were conducted at the same locations as that of the ATCs locations, in order to provide vehicle classification data and to compare overall traffic volumes with the ATCs. These were followed by 7 additional MCLCs, surveyed for two days in locations where an ATC had not taken place (item 10 of Table 2-7). Manual Classified Turning Counts (MCTCs) were undertaken (item 4 of Table 2-7) on a single neutral weekday in September 2017 at the major roundabouts and junctions. Other ad-hoc surveys were also undertaken, such as a minor access survey and weaving survey to provide further information to inform the ongoing development of the Scheme design. Journey time data Ten strategic journey time routes were identified for the purpose of validating the traffic model (shown in Figure 2-6). Trafficmaster journey time data collected in June 2015 (item 3 of Table 2-6) was used to validate the modelled journey times across these routes. As well as the ten strategic key routes identified for model validation, a further set of seven competing ‘rat run’ routes were identified on more local roads where traffic flows could be affected by the Scheme improvement. These routes (generally east to west within the corridor of the Scheme) have also been used to validate the modelled journey times and are shown in Figure 2-6 and Figure 2-7. Further details are in the TDCR, paragraphs 3.4.6 to 3.4.12.

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Routes 15 a and b Routes 16 a and b Routes 17 a and b

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2.6 ComMA data requirements Table 2-8 references the data used in the development of the transport models.

Table 2-8: ComMA Data Requirements Summary – Chapter 2

ComMA Reference to ComMA Package Requirement

Stage 3 Transport Data Package: Traffic Data Collection Summary and review Report (TDCR), January 2021, (Included as Appendix A of of existing data this Report). Chapter 3, covers the data which was collected and reported on at PCF Stage 1/2.

The Appendix A of the ComMA, Stage 3 Transport Data Package: Traffic Data Collection Report (TDCR), January 2021 contains details of data collected for PCF Stage 3. Specifically: Chapter 4 – Specification and execution of surveys Data collection Chapter 5 – Observed Automatic Traffic Counts Chapter 6 – Observed Manual Classified Surveys Chapter 7 – Automatic Number Plate Recognition Chapter 8 – Other Survey Data

The Appendix A of the ComMA, Stage 3 Transport Data Package: Traffic Data Collection Report (TDCR), January 2021 contains details of the final datasets for PCF Stage 3. Specifically: Appendix A – Survey Site Locations by Proposed Model Screenlines & Cordons Final data sets Appendix B – Summary of Model Input Flows Appendix C – Journey Time Routes Derived from Trafficmaster Data Appendix D – Summary of Incidents Appendix E – July / September 2018 Site Comparison Appendix F – Re-issued Sites Comparison

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3 Model development

3.1 Introduction A traffic model had been developed for the appraisal of options for the Scheme as part of PCF Stage 2. This was a strategic transport model based on an interim development version of Highways England’s South East Regional Traffic Model (SERTM). An updated version of the Stage 2 model, known as Stage 2+ was prepared and used to provide forecasts for the public consultation in 2019. A number of enhancements were made to create the Stage 2+ model as follows: a. Updating the inter-peak matrices around the Buckden area that were resulting in high volumes on roads in the vicinity and high delays, particularly on the A. b. Updating zone loading to reduce delays in Royston, Stevenage, Hitchin and along the A507. c. Updating the model network. d. Updating components of the demand model. e. Using a more recent version of the SATURN software. For PCF Stage 3 it was considered that a new traffic model should be developed to expand on the area that the PCF Stage 2 model covered. This would also enable more recent and robust traffic demand data to be utilised and to assess the potential impacts of relevant highway schemes across a wider area. The Stage 3 traffic model was therefore developed to assist in the traffic modelling and assessment of the Scheme. This chapter summarises the work carried out in the development of the Stage 3 2015 Base Year (BY) model, hereafter referred to as the A428 Strategic Traffic Model. A full description of the development of the A428 Strategic Traffic Model is provided in the Local Model Validation Report (LMVR) which is included as Appendix B of this report.

3.2 Overview of the A428 strategic traffic model The development and refinement of the modelling to provide an evidence base for PCF Stage 3 and the DCO application comprises two main components: a refined version of the SERTM (known as the A428 Strategic Traffic Model) and a number of newly developed operational models. The primary use of the A428 Strategic Traffic Model is to assess the traffic impacts of the A428 Black Cat to Caxton Gibbet Improvements scheme and to provide inputs into economic and environmental appraisals, as well as informing the buildability (construction traffic management) of the Scheme and operation and design of its junctions.

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The model may also need to be able to undertake bespoke sensitivity tests at the request of stakeholders to provide additional supporting information – either as part of the DCO examination or for separate supporting activities. It is likely that the model will also be used in the future as part of a monitoring and evaluation strategy for the Scheme. For many of the construction and design focused activities for which traffic data are required, traffic data from the model has been used as an input into more specialised operational models. Separate microsimulation models have been designed for this purpose. The traffic assignment model was built in SATURN version 11.4.07H. The SATURN network was initially formed by combining and modifying the Stage 2 2016 Base Year model network, within the Area of Detailed Modelling (AoDM), and the SERTM 2015 Base Year network. The behavioural responses to changes in travel costs were carried out by modelling the ‘variable demand’ impacts of trip re-distribution, trip frequency and mode shift in addition to route choice. The highway assignment model was therefore linked to the Dynamic Integrated Assignment and DEmand Modelling (DIADEM)18 software so that this range of possible responses could be represented in the study’s forecasts. Details of the model development and key parameters are given in Chapter 4 of the Stage 3 Transport Model Package: Local Model Validation Report (LMVR), Appendix B to the ComMA. Details of the Variable Demand Model are presented in Chapter 12 of the LMVR.

3.3 The A428 strategic traffic model Model structure The A428 Strategic Traffic Model developed for the Scheme is a significant change to the PCF Stage 2/2+ model drawing upon the SERTM model (Design Freeze (DF) 4) maintained by Highways England to expand the geographic scope. The A428 Strategic Traffic Model is the highway assignment component of the wider Regional Traffic Model (RTM) suite. Highways England developed the RTM model suite to provide an evidence base for the future development of schemes on its SRN as part of the RIS process. The suite of models follows the principles set out in the DfT’s Transport Analysis Guidance (TAG), comprising: a. A trip-end model, used for estimating the number of trips generated / attracted by a specific zone. Base year demand has been refined as part of the PCF Stage 3 works.

18 Department for Transport (DfT) software to enable users to easily set-up variable demand models in accordance with the advice provided in TAG.

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b. A Variable Demand Model (VDM), used for estimating how travellers will respond to changes in their travel costs, including modal considerations. c. A Highway Assignment Model (HAM), used for estimating travel costs and identifying the routes travellers may take through a congested road network. Figure 3-1 provides an overview of the model structure.

Figure 3-1: Regional Traffic Model (RTM) Suite Design There is not a public transport model network, but the VDM does incorporate a demand model choice hierarchy including car and public transport (rail) mode choice at the second level of the hierarchy. Public Service Vehicles (PSVs), which include buses and coaches, in or between Bedford, Huntingdon, St Neots and Cambridge were extracted from the Cambridge Sub-Regional Model (CSRM) and Bedford Transport Model and coded as fixed flows in the A428 Strategic Traffic Model. Spatial coverage The spatial coverage of the model is shown in Figure 3-2. This shows the network coding has been broadly split into three categories: simulation inside the AoDM which includes detailed junction coding as highlighted in orange (and outlined in purple) of local and major routes; simulation outside the AoDM (consistent with the SERTM modelling of ‘B’ roads and above) as highlighted in blue; and buffer (fixed speed/flow curves) as highlighted in grey. The buffer network extends to cover the wider UK SRN.

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Contains Ordnance Survey Data © Crown Copyright and database right 2019 Figure 3-2: A428 Strategic Traffic Model Network Coding Level of Detail

Base year and time periods The model Base Year was defined as 2015 which is consistent with SERTM19. As the Black Cat ‘Pinch Point’ improvement scheme opened on 27 March 2015 resulting in some significant increases in traffic over the following few months, the model was calibrated and validated to an equivalent June 2015 weekday. To allow consistency with SERTM, the Base Year models were built to represent an average peak hour for the following weekday time periods: a. Morning (AM) peak: an average hour of 07:00 - 10:00/ b. Interpeak (IP) peak: an average hour of 10:00 - 16:00/ c. Evening (PM) peak: an average hour of 16:00 - 19:00. An analysis of the morning peak period flows was carried out. A total of 20 WebTRIS sites on the SRN were selected for comparison of the three-hour Average Weekday Traffic (AWT) flows between 06:00 – 09:00 and 07:00 – 10:00. This showed that most of these sites have higher flows between 07:00 to 10:00, confirming that the AM peak period of the A428 Strategic Traffic Model was correctly defined.

19 SERTM Base Year model represents average weekday conditions in 2015 March

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User and vehicle classes The Base Year model was built based on the three vehicle classes in accordance with Department for Transport, National Road Traffic Census, Vehicle Classification Guidance 2018 and the Highways England’s Cost Benefit Analysis (COBA) classifications, as identified below: a. Vehicle Class 1: Cars. b. Vehicle Class 2: Light Goods Vehicles (LGV): up to 3.5 tonnes gross vehicle weight. c. Vehicle Class 3: Heavy Goods Vehicles (HGV), including: i. OGV1: Other goods vehicles, greater than 3.5 tonnes, up to 3 axles. ii. OGV2: Other goods vehicles, greater than 3.5 tonnes, 4 or more axles and all articulated goods vehicles. Car trips were defined by one of three trip purposes which are classified as User Classes in the model, as per the existing SERTM matrices to facilitate matrix development. This is shown in Table 3-1, together with the corresponding Vehicle Classes:

Table 3-1: Model User Classes and Vehicle Classes

User Class Vehicle Class Purpose

1 1 Car Employer’s Business

2 1 Car Commuting and Education

3 1 Car Other Purposes

4 2 LGV

5 3 HGV (OGV1 and OGV2)

3.4 Guidance applicable for development The network coding is consistent with Highways England’s Regional Traffic Models (RTM) Network Coding Manual, Version: 0.8, December 2015. The DfT’s guidelines have been used as a measure of the Base Year model calibration and validation in terms of link flow, screenline (SL) and journey time (JT) route comparisons (modelled versus observed), as well as model convergence criteria. These include: a. TAG Unit A1.3: User and Provider Impacts (March 2017). b. TAG Unit M1.2: Data Sources and Surveys (January 2014). c. TAG Unit M2: Variable Demand Modelling (May 2019). d. TAG Unit M3.1: Highway Assignment Modelling (January 2014). e. TAG Unit M4: Forecasting and Uncertainty (May 2019).

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f. TAG Databook (May 2019 Databook provided by DfT).

3.5 A428 strategic traffic model development Area of Detailed Modelling (AoDM) Initial assessments were undertaken to determine the Likely Region of Impact (LRoI) using the Stage 2+ model in accordance with TAG Unit M3.1 §2.2.1 and §2.2.5. The LRoI is defined as the area over which the preferred route may have significant impacts. Consideration was given to potential air quality and noise impacts as well as potential traffic volume and speed changes. The Area of Detailed Modelling (AoDM) of the A428 Strategic Traffic Model was developed based on the Stage 3 cordon of traffic surveys undertaken in 2017, within the LRoI. Figure 3-3 illustrates the extent of the AoDM. The AoDM extends to the A1(M) J14 to the northwest of Huntingdon, the A428 to the west of Bedford and the A14 / A11 junction to the east of Cambridge. It extends southwards to include the A507 / A505 routes between Milton Keynes and Cambridge.

Contains Ordnance Survey Data © Crown Copyright and database right 2019 Figure 3-3: Boundary of Area of Detailed Modelling

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Local zoning The zoning system was derived from that used in SERTM but significantly altered within the AoDM and in the buffer area of the A428 Strategic Traffic Model. Within the AoDM area zones are more disaggregate than SERTM being based upon the zoning used in the Stage 2 model. Where appropriate the boundaries of zones were redefined to better reflect Middle Layer Super Output Area (MSOA), Lower Layer Super Output Area (LSOA) or Output Area (OA) boundaries and where required these zones were disaggregated. Development zones have been defined where necessary to enable the demand generated by significant proposed developments to be assigned to the highway network separately from existing nearby settlements. These zones were additional to the existing zoning, and their boundaries did not necessarily follow the MSOA, LSOA or OA systems. SERTM zones have been used in the areas immediately outside the AoDM. This also included the arc of MSOAs through Oxfordshire, Buckinghamshire and Milton Keynes to enable better representation for assessing the proposed full Oxford-Cambridge Expressway scheme in the future. In areas further afield the SERTM zones have been aggregated to district level. The zoning system for the AoDM is shown in Figure 3-4.

Contains Ordnance Survey Data © Crown Copyright and database right 2019 Figure 3-4: Zone System for Area of Detailed Modelling (AoDM)

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Matrix development A key objective for the A428 Strategic Traffic Model was to improve the representation of local trip movements. The starting point for the demand matrix was SERTM for Design Freeze 2 (DF2)20. A series of local adjustments were then made to improve the accuracy of the prior matrix in the A428 model area. The first stage of the process involved the conversion of the prior (pre-matrix estimation) SERTM demand matrices to a new zoning system for the A428 model. This was considerably more detailed in the AoDM and aggregated further away from this area. The external zones (outside the South-East area) were unchanged from those in the SERTM. A preliminary assignment was carried out using the re-zoned matrices. This highlighted the following issues: a. A general shortfall in freight trips, these are fairly consistent across different movements for LGV but more variable for HGV. b. A consistent shortfall of traffic along Screenline 1, shown in Figure 3-5. c. Imbalances in modelled versus observed vehicle type proportions in Screenline 6 around St Neots.

Contains Ordnance Survey Data © Crown Copyright and database right 2019 Figure 3-5: A428 Strategic Traffic Model Survey Cordon and Screenlines

20 Design Freeze (DF) DF3 was the final prior matrix of the South East Regional Traffic Model (SERTM) at the time of the analysis, but DF2 was used as the DF3 matrix had been simplified to fit within the practical constraints of the SERTM SQL Server database.

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Local adjustments were then made to the re-zoned matrices to improve the accuracy of the prior matrix in the A428 model area. a. Use of roadside interview data from a cordon around St Neots (which is very close to the Scheme) was merged with DF2 SERTM demand to improve confidence in the matrix around this area (full details given in Section 7.2 of the LMVR, Appendix B to the ComMA). b. Global adjustment for freight demand (Light and Heavy Goods Vehicles), on evidence from observed count data that there was a notable understatement of freight traffic in this area in SERTM DF2 (full details given in Section 7.3 of the LMVR, Appendix B to the ComMA). c. Re-estimation of short trips (car, all purposes, although excluding very short trips of less than 1km) using synthetic demand. This was a revised infilling of short distance car trips, undertaken based on Census Journey to Work and National Travel Survey (NTS) data (full details given in Section 7.4 of the LMVR). d. Factoring of specific origin-destination zone pairs to improve the validation of the A421 flows in the internal area. Flows on the A421 were low in all time periods and user classes at three different locations (West of Bedford, through Bedford and East of Bedford), so select link analysis was used to identify and adjust zone pairs for improvement, calibrated to produce the best flow validation on the A421 (full details given in Section 7.5 of the LMVR). e. Considering, and rejecting, use of Traffic Information System (TIS) data. TIS comprises mobile network data compiled on behalf of Highways England for general use, but no strong reasons were found to use it in place of DF2 data, so it has not been used in the A428 model prior matrices. Network development The network for the A428 Strategic Traffic Model was created by combining the simulation links in the AoDM from the A428 Stage 2 2016 Base Year model with the network outside of the AoDM from the SERTM 2015 Base Year model. The RTM Network Coding Manual was used as a guide to the network coding, to ensure consistency in terms of the coding of the saturation flows, minimum gap values accepted by a vehicle which gives way at a junction and roundabout capacities. As part of the network development process, checks of significant warnings, such as link distances against crow-fly distance and distances/speeds being different by direction were made. A detailed coding audit was conducted of the strategic network in the AoDM including junction coding, with checks on the link lengths, number of lanes and merge (M) and queue (Q) markers. Further adjustments were also undertaken as part of the model calibration process, described in Section 3.6 of the ComMA. These adjustments included: zone loading; signal timings; lane arrangements; saturation flows; and link speeds.

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Assignment method The assignment of trips to the highway network has been undertaken using a user-equilibrium assignment which determines the routes chosen by drivers travelling from a given origin to a given destination. User-equilibrium, as implemented in SATURN, is based on the Frank-Wolfe algorithm, which employs an iterative process based on successive all-or-nothing assignments to generate a set of combined flows on links that minimise an objective function. The travel costs are re-calculated at each iteration and then compared to those from the previous iteration. The process is terminated when the costs obtained from successive iterations do not change significantly. At this point, the model is considered to have converged to a pre-defined degree. As the modelled time periods all cover a single average hour over a three (AM and PM peak) or six-hour period (interpeak), there is no requirement to model a pre-peak hour through a proxy assignment. Therefore, no passing of queues (a ‘PASSQ’ assignment) is undertaken. Generalised costs Route choice in the assignment model is based on the generalised cost, a combination of travel time, vehicle operating costs and any tolls or charges. Within the highway assignment model, the value of time (VoT) is expressed as the pence per minute (PPM), whilst the vehicle operating cost (VOC) is expressed as the pence per kilometre (PPK). The VoT and VOC used in the Base Year model have been calculated based on the TAG Databook released in May 2019 and are shown in Table 3-2. The value of time applicable to HGV trips has been uplifted by a factor of two as suggested in TAG Unit M3.1 paragraph 2.8.8. The VOC calculation has been based on an average speed of 65kph in the simulation network as modelled.

Table 3-2: Values of Time and Vehicle Operating Costs

AM Peak Interpeak PM Peak User Class PPM PPK PPM PPK PPM PPK

1: Car Employer’s 29.94 11.92 30.68 11.92 30.37 11.92 Business

2: Car Commute 20.08 5.85 20.40 5.85 20.14 5.85

3: Car Other 13.85 5.85 14.75 5.85 14.50 5.85

4: LGV 21.16 13.53 21.16 13.53 21.16 13.53

5: HGV 42.96 36.66 42.96 36.66 42.96 36.66

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3.6 Calibration and validation Calibration and validation approach The primary focus of the A428 Strategic Traffic Model calibration and validation is in the AoDM, with the aim of ensuring an appropriate representation of trips on the A421 / A428 and the local road network in the vicinity of the Scheme. A staged approach to model calibration and validation was undertaken. Calibration and validation of the highway networks was carried out initially. This was followed by an assessment of the matrix performance with any subsequent updates made via a process of matrix calibration. Further refinements were carried out as part of the assignment calibration. Network calibration After the network development (which included checks of significant SATURN network warnings; a detailed coding audit of the strategic network in the AoDM; and review of all junction nodes updated for the A428 Strategic Traffic Model), further adjustments were subsequently made as part of the model calibration process. Network calibration was undertaken to identify issues in the model such as unrealistically long delays, excessive queues and unrealistic speeds. After initial assignments were carried out, checks were specifically undertaken where the model was predicting significant delays and/or large differences between demand and actual flows, which can be an indicator of issues with simulation coding and incorrect junction coding. A thorough review of the network coding was carried out in locations where significant delays were predicted in order to determine whether the delays were valid. This included saturation flows, flares at turns and Speed-Flow Curves (SFCs), as well as zone connectivity in relation to zone size and location/catchment, and local assignment routing. The network detail in Milton Keynes was also improved, although it is outside the AoDM. All the significant delays inside the AoDM were addressed. Due to the less detailed nature of the network outside the AoDM (the area extracted from the SERTM), there were still a few significant delays which were not completely resolved. However, since they were located remote from the AoDM, Hemel Hempstead being one area, these were not considered to be significant in terms of impacts on the Scheme. This process improved the accuracy of the network and modelled journey times. The route choice calibration and validation consisted of checking that routes taken were logical and to make adjustments to the model where necessary. This involved identifying where a poor comparison between observed and modelled flows may have been caused by unrealistic routeings through the network. Where routeings were considered unreliable, various adjustments to speed/flow curves and junction coding were made to improve the model representation. The details are provided in Chapter 9 of the Local Model Validation Report (LMVR), Appendix B to the ComMA.

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Matrix calibration Matrix calibration is an iterative process that involves reviewing and adjusting the model’s trip matrices so that modelled traffic flows, speeds, junction delays and routeings through the network provide a reliable match with observed data. The initial process of producing and refining the prior matrix, which is the matrix before calibration is applied via matrix estimation, is outlined in paragraph 3.5.11 above. Full details of the process are provided in Chapter 7 of the LMVR. Model calibration of the prior matrix, followed a two-stage process: a. The modelled flows produced using the prior matrices were compared with observed data. This included using individual link flows, screenline flows and journey times. b. The matrix was then adjusted using Matrix Estimation (ME). Further network edits were also carried out where appropriate, to reduce differences between the modelled and observed data to more acceptable levels, using the criteria in TAG, detailed in Chapter 3 of the LMVR, that form part of the Traffic Modelling Package. ME was undertaken using the SATURN modelling software after network checks had been carried out. The ME process adjusts the matrices by factoring up or down origin and destination pairs in the prior matrices with the aim of improving the match between observed and modelled flows at a series of observed count locations. As ME is a mathematical process that relies on assignments to adjust the matrices, it is typically used for refinement rather than wholesale changes. The ME process was carried out in accordance with Section 8.3 of TAG Unit M3.1, Highway Assignment Modelling (January 2014). The process is illustrated in Figure 3-6.

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Figure 3-6: SATURN ‘ME2’ Matrix Calibration Process Several assignments of the prior matrices using the three user classes were undertaken as part of the network checking and refining process. At this point the prior matrices were split into five user classes and run through the ME process. Matrix calibration results Calibration was monitored by reviewing the changes to the trip matrices resulting from the ME process, and by comparing observed traffic counts and modelled traffic flows expressed in Passenger Car Units (PCUs). The following measures were used to monitor the impact of the ME process for each of the modelled time periods: a. Comparison of calibration counts and modelled flows: scatter plots and regressions of modelled against observed flows;. b. Factored prior and post ME trip length distributions. c. Factored prior and post ME trip end scatter plots and regression statistics. The criteria used to judge the significance of the changes brought about by matrix estimation, are as referenced in Section 8.3 of TAG Unit M3.1, Highway Assignment Modelling (January 2014) and summarised in Table 3-3. This states that the changes should not be significant.

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Table 3-3: TAG Unit M3.1: Significance of Matrix Estimation Changes

Significance of Matrix Estimation Changes

Measure Significance Criteria

Slope within 0.98 and 1.02 Matrix zonal cell values Intercept near zero R2 in excess of 0.95

Slope within 0.99 and 1.01 Matrix zonal trip ends Intercept near zero R2 in excess of 0.98

Means within 5% Trip length distributions Standard deviations within 5%

Sector to sector level Differences within 5% matrices

The results of the matrix calibration process are summarised as follows: a. Trip Length Distribution (TLD) comparisons for the AM peak show that the overall relationships between the trip movements and distances travelled prior to and post-ME were very similar for car, LGVs and HGVs, and all are within an acceptable level of variation, with reference to TAG Unit M3.1, paragraph 8.3.15, Table 5. The results for the IP and PM peak models in Appendix C of the LMVR (the Appendix B to the ComMA) show very similar patterns. b. The matrix totals for each User Class and each time period (shown in Tables 10.6 to 10.8 of the LMVR) also demonstrate that the matrix totals were not significantly affected by the ME process. The overall percentage changes were small, AM -0.05%, IP -0.07% and PM -0.06%. c. Linear regression was undertaken between modelled and observed calibration volumes and showed that calibration was to a good standard with the R2 values being 0.9928, 0.9975 and 0.9975 for AM, IP and PM respectively (see Figure 10.2 to Figure 10.4 of the LMVR, Appendix B to the ComMA). d. Linear regression statistics from the comparison of pre- and post-ME trip ends inside the AoDM were also reasonably consistent with the requirements specified in Table 5 of TAG Unit M3.1 (Slope between 0.99 and 1.01; intercept near zero and R2 in excess of 0.98). While the slopes are marginally outside the recommended guidelines, the intercepts are relatively close to zero, and the R2 values conform to the criteria (see Table 10.9 of the LMVR, Appendix B to the ComMA). The results of the regression analysis are therefore considered good.

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e. Finally, the linear regression statistics from the comparison of pre- and post- ME matrix individual cell values by vehicle type show intercepts all very close to zero, with all gradients and R2 values meeting the criteria in Table 5 of TAG Unit M3.1. Additionally, the calibration acceptability guidelines for this model are those set out in Section 3.3 of TAG Unit M3.1 reproduced in Tables 3.1 and 10.2 of the LMVR (the Appendix B to the ComMA) for reference. Note that it is sufficient for the comparisons to pass either the GEH statistic21 criterion or the flow difference criterion. Screenline and link count performance details against TAG criteria are outlined in paragraphs 3.6.22 to 3.6.35. Two versions of ME were run. The ‘a’ version was run including the calibration screenlines only. The ‘b’ version utilised data from both the calibration and the validation screenlines within the calibration process. Therefore, in version ‘b’ there were no independent screenline data for validation. The version ‘b’ model was therefore validated using the journey time data only. The screenline performance for the validation screenlines was significantly improved by version ‘b’ (see further details in Chapter 11 of the LMVR, Appendix B to the ComMA). As agreed with Highways England, the ME run version ‘b’ using all calibration and validation screenlines was used as the final version of the Stage 3 Base Year model. Screenline performance The test of a model’s ‘fitness for purpose’ is carried out by examining the extent to which the model reproduces observed conditions. As part of this process the model output was reviewed against the observed count data to check the extent to which modelled screenlines total volumes match observed totals. The screenlines were also checked to determine the proportions of the calibration and validation links where modelled flows were close to those observed (using TAG criteria). The cordons and screenlines developed for the calibration and validation are shown in Figure 3-7. The survey cordon together with screenlines 1 to 7 were used for model calibration, and the data from screenlines 8 to 10 were set aside for validation for version a. For version b, the data for all screenlines were used in the model calibration process.

21 The GEH statistic gets its name from Geoffrey E. Havers. It is a form of the Chi-squared statistic that incorporates both relative and absolute errors, which is commonly used in highway modelling as an indicator of ‘goodness of fit’ between modelled flows and observed flows.

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Contains Ordnance Survey Data © Crown Copyright and database right 2019 Figure 3-7: A428 Strategic Traffic Model Cordon and Screenlines

Table 3-4 summarises the results of the comparison of observed and modelled flows on the calibration screenlines from 1 to 7 and cordon based upon version ‘a’, for all vehicles, by time period. Table 3-5 summarises the results on the validation screenlines from 8 to 10.

Table 3-4: Performance of Calibration Screenlines - Model Version ‘a’

Time Period No meeting TAG criteria % of total

AM peak 15 out of 16 94%

Inter-Peak 16 out of 16 100%

PM Peak 16 out of 16 100%

Table 3-5: Performance of Validation Screenlines - Model Version ‘a’

Time Period No meeting TAG criteria % of total

AM peak 4 out of 6 67%

Inter-Peak 1 out of 6 17%

PM Peak 4 out of 6 67%

The validation criterion and acceptability guideline for screenline flows is defined in Section 3.2.5 of TAG Unit M3.1. This states that the criterion acceptability guideline differences between modelled flows and counts should be less than 5% of the counts on all or nearly all screenlines.

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Table 3-4 and Table 3-5 show that the TAG criteria is satisfied for the calibration screenlines, whereas the performance on the validation screenlines was significantly below the TAG criteria. The results of the comparison of observed and modelled flows on the calibration screenlines (i.e. 1 to 7) and cordon based upon version ‘b’, for all vehicles, by time period, is summarised in Table 3-6. Table 3-7 summarises the results of version b on the validation screenlines (8 to 10).

Table 3-6: Performance of Calibration Screenlines - Model Version ‘b’

Time Period No meeting TAG criteria % of total

AM peak 15 out of 16 94%

Inter-Peak 16 out of 16 100%

PM Peak 16 out of 16 100%

Table 3-7: Performance of Validation Screenlines - Model Version ‘b’

Time Period No meeting TAG criteria % of total

AM peak 6 out of 6 100%

Inter-Peak 6 out of 6 100%

PM Peak 6 out of 6 100%

Table 3-6 and Table 3-7 demonstrate that the results for model version ‘b’, which included both the calibration and validation screenline counts in the ME process, shows a significant improvement compared to the ‘validation’ screenlines in model version ‘a’. All calibration and validation screenlines pass the assessment criteria in version ‘b’. The detailed results of the comparison on the cordon and individual screenlines is presented in Chapter 11 of the LMVR, Appendix B to the ComMA, that forms the Traffic Modelling Package. On the basis of these results, it was decided to adopt model version ‘b’ as the final version of the Stage 3 Base Year A428 Strategic Traffic Model. While it was acknowledged that by using all data in the calibration process there would be no independent count data available for validation, this was outweighed by the improvement in the quality of the final Base Year matrix where an excellent match with observed data was achieved. The results presented in the following paragraphs are therefore based on the adopted model version ‘b’. Link flow calibration and validation The TAG acceptability guidelines for modelled and observed link flow comparisons are shown in Table 3-8 for individual links and turning movements.

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Table 3-8: TAG Link Flow and Turning Movement Calibration/Validation Criteria and Acceptability Guidelines

Acceptability Criteria Description of Criteria Guideline

Individual flows within 100 veh/hr of > 85% of cases counts for counts less than 700 veh/hr

Individual flows within 15% of counts for > 85% of cases 1 counts from 700 and 2,700 veh/hr

Individual flows within 400 veh/hr of counts for observed flows greater than > 85% of cases 2,700 veh/hr

2 GEH statistic < 5 for individual flows > 85% of cases

Source: TAG Unit M3.1 Table 2 A comparison of the observed and modelled flows for the validation and calibration count sites are presented in Table 3-9, Table 3-10 and Table 3-11 for the AM, IP and PM time periods respectively.

Table 3-9: Total Calibration and Validation Counts (All Vehicles) – AM

All Sites Total no. of Counts Counts that pass %

Calibration Counts: Flows 264 251 95%

Calibration Counts: GEH 264 242 92%

Calibration Counts Either 264 252 95%

Validation Counts: Flows 63 63 100%

Validation Counts: GEH 63 61 97%

Validation Counts Either 63 63 100%

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Table 3-10: Total Calibration and Validation Counts (All Vehicles) – IP

All Sites Total no. of Counts Counts that pass %

Calibration Counts: Flows 264 260 98%

Calibration Counts: GEH 264 252 95%

Calibration Counts Either 264 260 98%

Validation Counts: Flows 63 63 100%

Validation Counts: GEH 63 62 98%

Validation Counts Either 63 63 100%

Table 3-11: Total Calibration and Validation Counts (All Vehicles) – PM

All Sites Total no. of Counts Counts that pass %

Calibration Counts: Flows 264 256 97%

Calibration Counts: GEH 264 243 92%

Calibration Counts Either 264 256 97%

Validation Counts: Flows 63 63 100%

Validation Counts: GEH 63 60 95%

Validation Counts Either 63 63 100%

The results of the link flow comparison show that the TAG link flow criteria are achieved in each time period. The detailed results are reported in Appendix D and Appendix E of the LMVR, which form part of the Traffic Modelling Package. Journey time calibration and validation Journey time comparisons were used as part of the model calibration process. Where large differences were identified at certain points along a journey time route, steps were taken to understand and address the cause. This included adjusting the speed/ flow curves to better represent the road type or speed limits in place. Where there was an issue at a particular signalised junction across time periods the saturation flows were checked, and signal timings adjusted appropriately. In order to validate the modelled journey times, they were compared to the observed journey time data extracted from Trafficmaster, as detailed in Chapter 2. These included 10 strategic routes and 14 competing routes, as illustrated in Figure 2-6 and Figure 2-7, in Chapter 2.

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For 98% of journey time routes the modelled journey time was within 15% of observed times (or 1 minute, if higher than 15%) for all three time periods (AM, IP and PM). This meets the acceptability guidelines for journey times defined in Table 3 of TAG Unit 3.1. It is noted that there is only one route failing in the AM peak and PM peak periods; route 16a (WB), which follows the B1428 / A428 from Caxton Gibbet to St Neots town centre. This route has a modelled journey time of 13 minutes 29 seconds; 15.9% higher than the observed time of 11 minutes 38 seconds. This route therefore only just fails the 15% threshold specified in TAG. All the journey time routes in the interpeak period passed the criteria. A detailed analysis of the journey time validation for each route is presented in Tables 11.19 to 11.21 in the LMVR. Additionally, Figures 11.1 to 11.6 in the LMVR provide journey time comparison plots for Route 1, A421 / A428 from M1 J13 to M11 J14 via the Black Cat (BC) roundabout, and the reverse route. The complete set of journey time plots are included in Appendix F of the LMVR. Model convergence Convergence is a key indicator of the stability of a model to determine that it can provide consistent and reliable results. There are several measures used to monitor convergence within the SATURN assignment model, including: a. Parameter %FLOW – this measures the percentage of links on which flows vary by more than a pre-defined percentage between consecutive assignment iterations. b. Parameters RSTOP, PCNEAR and NISTOP – set to 99, 1 and 4 respectively for the A428 Strategic Traffic Model, which between them define convergence as being met when link flows on 99% of all links in the network vary less than 1% for four consecutive iterations. These convergence criteria are more stringent than the TAG criteria given in Unit M3.1 (also reproduced in Tables 3.3 and 11.2 of the LMVR, Appendix B to the ComMA). TAG provides further guidance on model stability in Appendix C of TAG Unit M3.1, which suggests other appropriate parameters to measure convergence, including: a. Average Absolute Difference (AAD) in link flows between consecutive iterations. b. Relative Average Absolute Difference (RAAD) in link flows between iterations, with the latter being the preferred measure with a target value of 0.1%.

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The A428 Strategic Traffic Model convergence statistics are presented in Table 3-12. This demonstrates that the model converges well in all three time periods.

Table 3-12: Highway Model Convergence Results

Assignment % % GAP AAD RAAD Loop Flows

AM 0.0030 0.18 0.020 99.1

IP 0.0015 0.19 0.026 99.3

PM 0.0025 0.17 0.020 99.3

Table 11.23 to Table 11.25 in the LMVR, Appendix B to the ComMA, show the full convergence statistics for the AM peak period, interpeak period and PM peak period respectively.

3.7 Variable demand model The A428 Black Cat to Caxton Gibbet improvements scheme VDM has been designed to estimate the effect of changes in transport infrastructure and travel cost upon patterns of demand. That is, the way travellers respond to changes other than choosing different routes, which is forecast by the highway assignment model. The advice in TAG Unit M2 has been adhered to in the development of the VDM. The VDM is tour-based. That is, it considers complete journeys starting and ending at the travellers’ home-base, visiting their “attraction”, or activity they are travelling for. This results in a linked chain of two trips by the same individual. The VDM uses a hierarchical logit structure (as shown in Figure 3-8), with the following choice models in order of increasing sensitivity: a. Time Period Choice. b. Car versus public transport mode choice. c. Attraction choice (trip distribution). The choice models are applied to person trips. The full choice hierarchy is illustrated below. Freight and port trips do not apply in any of the choice models.

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Figure 3-8: Demand Model Choice Hierarchy The VDM is a pivot-point incremental model which estimates changes in trip patterns relative to a ‘reference’ matrix based upon observed data. In other words, the VDM seeks to forecast changes in demand in response to changes in cost, rather than attempting to estimate all demand based purely on the costs of travel. This is generally recommended by TAG Unit M2. In forecasting mode, when running any test, the VDM will pivot from the Base Year model, evaluating cost changes relative to the Base Year and adjusting the reference demand matrix accordingly. The VDM responds to changes in generalised cost. For the highway generalised cost, the functions derived from TAG Unit M2 are used. The parameters used in these functions have been derived directly from the TAG Databook (May 2019). Full details of the development of the VDM are provided in Chapter 12 of the LMVR.

3.8 ComMA data requirements Table 3-13 summarises the relationship between the ComMA report and ComMA Packages for information in Chapter 3, and identifies where further information can be found in relation to data used in the development of the transport models.

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Table 3-13: ComMA Data Requirements Summary – Chapter 3

ComMA Reference to ComMA Package Requirement

The Appendix B of the ComMA, Stage 3 Transport Model Package Local Model Validation Report, January 2021. Specifically: Model Description / Chapter 2 – Model Requirements and Design Considerations Specification Chapter 3 – Modelling Standards Chapter 4 – Key Features of the Model

The Appendix B of the ComMA, Stage 3 Transport Model Package Local Model Validation Report, January 2021. Specifically: Chapter 2 – Model Requirements and Design Considerations Model Development Chapter 3 – Modelling Standards Chapter 4 – Key Features of the Model Chapter 6 – Network Development Chapter 7 – Trip Matrix Development

The Appendix B of the ComMA, Stage 3 Transport Model Package Local Model Validation Report, January 2021. Specifically: Chapter 5 – Calibration and Validation Data Model Calibration Chapter 8 – Network Calibration Chapter 9 – Route Choice Calibration and Validation Chapter 10 – Trip Matrix Calibration and Validation Chapter 11 – Assignment Calibration and Validation

The Appendix B of the ComMA, Stage 3 Transport Model Package Local Model Validation Report, January 2021. Specifically: Chapter 5 – Calibration and Validation Data Model Validation Chapter 9 – Route Choice Calibration and Validation Chapter 10 – Trip Matrix Calibration and Validation Chapter 11 – Assignment Calibration and Validation

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4 Forecasting

4.1 Introduction This Chapter describes the development of the traffic forecasts prepared for the assessment of the the Scheme. It details the assumptions that have been used to create the forecasts, including the Uncertainty Log (UL), which pulls together the future year planning data and infrastructure changes. Further details are provided in the Traffic Forecasting Report (TFR) which is included as Appendix C to this report. Traffic forecasts were required to determine the impacts of the Scheme on the A428, A1, A421, surrounding local road network and on other strategic routes. Forecast traffic volumes were used to inform. a. The extent to which the Scheme addresses the identified transport problems; b. Scheme design standard requirements (for example, against the Design Manual for Roads and Bridges (DMRB) criteria for number of lanes, junction types, road standard). c. the Environmental Statement (ES) to determine the impacts of changes brought about by the Scheme on air quality, noise pollution, health impacts and biodiversity assessment amongst others. d. The impacts of proposed construction and traffic management plans. e. An assessment of the economic benefits of the scheme including transport user benefits, accident and wider benefits. Process The development of forecasts was based upon the following process: a. Creating reference demand for travel, reflecting forecast changes to land use and demographics. b. Developing a representation of the without-scheme highway network and rail costs. c. Applying the reference demand to the without-scheme highway network within the demand model. d. Adjusting the forecast travel demand based on changes to cost of travel and land use in the without-scheme scenario. e. Developing a representation of the with-scheme network. f. Adjusting the forecast travel demand based on changes to cost of travel and land use in the With-Scheme scenario.

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4.2 Assumptions Forecast years Traffic forecasts have been developed for the following forecast years: a. 2025 - Opening year. b. 2040 - Design year (15 years after the Scheme opening). c. 2051 - Horizon year for economic appraisal, reducing uncertainty in extrapolation from 2040 to the end of the 60-year appraisal period. The National Trip End Model (NTEM) dataset is not available post 2051. Uncertainty Log (UL) An Uncertainty Log (UL) was created to record the central forecasting assumptions that underpin the core scenario and record the degree of uncertainty around these central assumptions. This required an understanding of which key factors will be subject to change between the Base Year and the Forecast Year. The UL is included as Appendix A of the TFR. The UL assumptions are detailed in Section 4.5 of the TFR, Appendix C to the ComMA. The UL study area covers a total of 25 Local Planning Authorities (LPAs). The LPAs and their respective highway authorities considered within the UL are outlined in Figure 4-1.

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The local demand section of the UL has been populated from a range of local authority information in order to capture all known proposed and planned developments across the study area. A list of the documents used to compile the UL is given in Table 4-2 of the TFR, Appendix C to the ComMA. All land use developments identified during the forecasting process were considered to be independent of the Scheme. There is therefore no dependent development22 associated with the Scheme. The local supply section of the UL was populated with a range of different transport schemes that are both in the planning stage or construction phase. These schemes were drawn from a number of different sources including local highway authorities and Highways England. The UL includes transport scheme information from the sources listed in Table 4-4 of the TFR, Appendix C to the ComMA. The highway network was developed, following the UL guidance set out in TAG Unit M4. Large development sites NTEM uses national average trip-rates that are low by the standard of trip-rates usually observed or forecasts at new developments. Consequently, the transport assessments for several key large developments in the model were inspected to extract the trips forecast by the developers specifically for these developments. The developments considered, and the trip rates extracted, are summarised in Table 5-12 of the TFR, Appendix C to the ComMA. New, large development sites can also be problematic in forecasting in the absence of demand in the Base Year. This can result in very large growth factors and unreliable trip distributions. This problem was addressed at several stages of the reference demand development through: a. A gravity model, used to estimate trip distributions for large development sites with little Base Year demand. Further details of the gravity model are given in paragraphs 5.3.12 to 5.3.16 of the TFR, Appendix C to the ComMA. b. Infilling factors to split all day to time period trips estimated from very low levels of base demand for large development sites. Reference demand for person related travel TAG Unit M4 defines reference forecasts as an intermediate step to producing the without-scheme and with-scheme forecasts. Reference demand is defined as the expected traffic demand if travel costs were not to change from their Base Year level.

22 Refer to Transport Analysis Guidance (TAG) Unit A2.2, Dependent developments are new residential or non-residential developments which require a complementary transport investment to receive planning approval.

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The development of forecast travel demand matrices for the A428 Strategic Traffic Model made use of national published growth forecasts from two sources; the NTEM (version 7.2), and the Road Traffic Forecasts (RTF) 2018. The NTEM was developed and is maintained on behalf of the DfT. It provides forecasts of personal trip-ends by Middle Super Output Area (MSOA), covering highway, public transport and walk/cycle modes, by purpose of travel and time of day. NTEM considers changes in population and employment at Local Authority level and changes to economic factors such as household incomes at the national level. For the A428 Strategic Traffic Model, an adaption of NTEM was prepared with a zone system consistent with the A428 Transport Model – namely, a hybrid of the A428 transport model zone system and the NTEM 7.2 zone system (Middle Super Output Areas, or MSOAs). The NTEM 7.2 planning data set (published in February 2017) was interrogated via the Trip End Model Presentation Program (TEMPro) to identify growth in the population, households and jobs for each district for each LPA. The trip-end forecasts from the A428 Strategic Traffic Model were constrained to the NTEM forecasts, in accordance with guidance in TAG Unit M4 paragraph 7.1.7. This is implemented by calculating the UL growth, adding it to the base year and then constraining it to NTEM growth at local authority level. The process was achieved using the following methods: a. Method 1 - where the absolute local plan growth was higher than NTEM. [Constrained FY] = [NTEM BY] + [UL Growth] * Factor, where Factor = ([NTEM Growth])/ [UL Growth]. b. Method 2 - when the absolute local plan growth was lower than NTEM. [Constrained FY] = ([NTEM BY] + [UL Growth]) + [NTEM Growth] * Factor, where Factor = ([NTEM Growth] - [UL Growth]) / [NTEM Growth]. c. Method 3 - when NTEM and local plan growth had different signs (for example, NTEM forecasts a decrease in trips and local plan growth an increase). [Constrained FY] = ([NTEM BY] + [UL Growth]) * Factor, where Factor = [NTEM FY] / [UL FY]. In summary, to create the reference demand for person-related travel: a. The base (2015) population / employment data is based on NTEM 7.2. b. The population / employment growth for the forecast years is taken from the Uncertainty Log, which is informed from local planning assumption data. c. Trip rates for key large developments in the model area are adjusted, as the average growth in trip rates forecasts by NTEM is considered as being too low to reliably represent these. d. The overall growth from the trip end model (to which the population / employment data is input) for all forecast years is constrained to NTEM 7.2, including large developments.

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Reference demand for freight The Road Traffic Forecasts (RTF) 2018 were used for freight forecasting (including to and from seaports). The RTF 2018 are produced on behalf of the DfT using the National Transport Model (NTM) and forecast traffic (i.e. road vehicle flow) growth. These have been used to apply growth to freight vehicles (Light Goods Vehicles and Heavy Goods Vehicles) in the model, because NTEM does not cover freight travel. RTF 2018 has been used to generate growth factors, calculated by year for LGV and HGV matrices, as presented in Table 5-4 of the TFR, Appendix C to the ComMA. These were applied directly to the Base Year freight matrices to create the future year demand. Demand forecasting – variable demand and generalised cost changes Having produced the reference demand for person-related travel, the variable demand model (VDM) applies changes in travel generalised cost to forecast changes in travel behaviour. The responses modelled include macro time period choice, mode choice and destination choice. Travel generalised costs are specified in terms of pence per minute (PPM) and pence per kilometre (PPK). The values used for each time period and forecast year are shown in Table 5-16 of the TFR. For highway assignment purposes, these differ by time period, whereas the variable demand model uses values at a daily level – as provided in Table 5-17 of the TFR, Appendix C to the ComMA. As the trip-end model and VDM only apply to personal travel, the remaining demand segments (port and freight demand) remain unchanged through the VDM process.

4.3 Forecast scenarios Without-Scheme network In accordance with TAG Unit M4 (Forecasting and Uncertainty), road schemes classified as being either ‘near certain’ or ‘more than likely’ have been included in the ‘core’ scenarios (both with and without the Scheme). Schemes categorised as either ‘reasonably foreseeable’ or ‘hypothetical’ have been excluded. There are also strategic road schemes that have either been completed since 2015 or are under construction. These schemes are also included in the ‘Without- Scheme’ scenario, known as the Do Minimum (DM) scenario. Highways England schemes being planned in Road Investment Strategy Period 1 have been included in the ‘core’ scenario In addition, a review of more local schemes in the vicinity of the AoDM was undertaken. This identified several schemes in the local area for delivery following the 2015 Base Year. These schemes are presented in Table 5-25 within the TFR, Appendix C to the ComMA, listed in priority of importance with relation to the A428 Strategic Traffic Model, which means the larger and more local the scheme to the Scheme, the higher the placement.

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With-Scheme network The With-Scheme (or Do Something / DS) network is as the Without-Scheme (or Do Minimum / DM) network, plus the proposed A428 Scheme. The Scheme includes the following changes to the Do Minimum network: a. The provision of a new 10 mile off-line 2-lane dual carriageway between Black Cat and Caxton Gibbet. b. Grade separation of Black Cat junction both east-west and north-south. c. The provision of a new grade separated junction at Cambridge Road. d. The enlargement and grade separation of Caxton Gibbet junction. e. The alteration of the B1040 east junction at Eltisley. f. The provision of a new road linking Roxton Road and Chawston Lane. g. The closure of the A1 junctions at School Lane, Chawston Lane and The Lane. h. The relocation of the junction of the B1046 St Neots Road and Potton Road. Low and high growth TAG guidance (Unit M4) discusses sensitivity testing for model forecasts. One key area of uncertainty is the level of growth in traffic, which encapsulates, among other things, uncertainty in GDP growth, fuel price trends and vehicle efficiency changes as forecast in the TAG Databook. Unit M4 advises on how to undertake sensitivity testing around this area. This involves executing “high” and “low” traffic growth sensitivity tests, with respectively higher and lower traffic growth than the core scenarios. The high growth scenario consists of forecasts that are based on a proportion (7.9%, 12.5% and 15% for the forecast years 2025, 2040 and 2051 respectively) of Base Year demand added to the demand from the core scenario. The low growth scenario uses the same proportion subtracted from the core scenario demand. A summary of the forecast scenarios modelled is shown in Table 4-1.

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Table 4-1: Summary of Forecast Scenarios

Model Scenario Demand Supply Years

Near certain and more than likely Near certain and more 1 Core developments. than likely infrastructure schemes. Constrained to NTEM.

2025 Proportion of Base Year demand added to 2 High growth 2040 As core scenario demand in the core 2051 scenario.

Proportion of Base Year demand subtracted from 3 Low growth As core scenario demand in the core scenario.

4.4 Annual Average Daily Traffic (AADT) and other time period factors For a number of processes traffic data is required for time periods other than those represented directly by the traffic model. The calculation of accident costs requires Annual Average Daily Traffic (AADT) flows which are also used for air quality assessment purposes. Noise assessment requires 18hr Annual Average Weekday Traffic (AAWT) and also evening and night-time volumes. For the purposes of this scheme, traffic data were analysed by four different road types as traffic profiles can be quite different between major and minor roads and between vehicle types. The four categories defined were: a. SRN (including the A428, A421, A1, A14 and M11 near the Scheme). b. ‘A’ Road (Non-SRN). c. ‘B’ Road. d. Other roads. The expansion factors were developed using available traffic data. This comprised continuous long term sites (mostly on SRN roads) sourced from WebTRIS, together with shorter duration 14 day ATC’s and MCLC’s that were undertaken specifically for the A428 Stage 3 assessment. As the models represent an average hour for the weekday peak and interpeak periods, the expansion factors from model hour to model period were the same for all road types, these being three for the AM and PM peak periods and six for the interpeak period. For periods outside these hours, factors differed by road type.

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As HGV volumes are of importance for the noise and air quality assessment, and their daily profile can be quite different to those of light vehicles, separate factors were derived for these vehicle types (presented in Table 4-3 and Table 4-2 respectively).

Table 4-2: Light Vehicle Expansion Factors

Interpeak 12hr 12hr 12hr Interpeak to AAWT to AAWT to AAWT to to Night Road Type Evening 24hr 24hr 18hr (23-7) (19-23) AADT AAWT AAWT AAWT AAWT

SRN 1.26 1.27 1.22 0.31 0.30

A Road (non- 1.13 1.23 1.20 0.33 0.24 SRN)

B Road 1.05 1.18 1.16 0.29 0.20

Other 1.05 1.19 1.17 0.31 0.17

Table 4-3: Heavy Vehicle Expansion Factors

Interpeak 12hr 12hr 12hr Interpeak to AAWT to AAWT to AAWT to to Night Road Type Evening 24hr 24hr 18hr (23-7) (19-23) AADT AAWT AAWT AAWT AAWT

SRN 1.16 1.44 1.24 0.23 0.57

A Road (non- 1.04 1.18 1.14 0.15 0.18 SRN)

B Road 0.95 1.10 1.08 0.09 0.09

Other 0.99 1.12 1.10 0.14 0.09

4.5 Traffic forecasting outcomes Model convergence The target measure of convergence should be the same for the ‘Without- Scheme’ and ‘With-Scheme’ assignments. This may require a different number of iterations for different network configurations and different matrices. Convergence is generally harder to achieve in congested conditions. Hence, more iterations may be required in the Without-Scheme network and in later forecast years.

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The purpose of the model is to assess the benefits and impacts of the Scheme. When comparing the impacts of a scheme in terms of traffic flows, journey times and economics, it is necessary to demonstrate that the differences between the ‘Without-Scheme’ and ‘With-Scheme’ assignments are the result of real changes and not the result of modelling noise. This dictates the requirements for convergence and stability. Table 6-2 and Table 6-3 of the TFR (the Appendix C to the ComMA) present the convergence statistics for the last four iterations of the DM and DS scenarios (Core growth) respectively. The statistics show that the relevant stopping criteria have been met for all model runs and that the %GAP is well under both the maximum permitted value of 0.1% and the desired value of 0.025%. Additionally, Table 6-4 and Table 6-5 of the TFR present the simulation network summary statistics for forecast years 2025 and 2040 respectively, including total trips assigned, vehicle hours, vehicle kilometres and average speeds. These statistics again demonstrate logical outcomes (described in more detail in Section 6.3 of the TFR, Appendix C to the ComMA). Forecast traffic flows This section details the forecast results and changes in traffic flows for major and local roads in the vicinity of the Scheme. The full set of AADT flow diagrams (in the form of schematic maps rather than SATURN graphical outputs) are presented in Appendix D of the TFR. Similarly, schematic maps of the average hourly flow data are given in Appendix F of the TFR, Appendix C to the ComMA. Figure 4-2 shows the sections of the Scheme links, for the A421, A1 and A428 from Black Cat to Caxton Gibbet for which flows are reported in detail. The Scheme has been divided into seven sections (A to G) for the existing route plus two sections for the new route (H and I), as identified in Table 4-4.

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Figure 4-2: Sections of Existing and Proposed Route

Table 4-4: The Scheme by Identified Sections

A421, West of Black Cat A1, North of Black Cat A B (Renhold junction to Black Cat) (Black Cat to Wyboston)

A428, West of Barford Road A428, East of Barford Road C (Wyboston to Barford Road D (Barford Road junction to junction) Cambridge Road junction)

A428, West of B1040 A428, West of Caxton Gibbet E (Cambridge Road junction F (Eltisley to Caxton Gibbet) to Eltisley)

A428, East of Caxton Gibbet New A428 Dual Carriageway G (Caxton Gibbet to Cambourne H (Black Cat to Cambridge Road junction) junction)

New A428 Dual Carriageway I (Cambridge Road junction to - - Caxton Gibbet)

Table 4-5 details the AADT forecasts for the existing A428 route sections that the Scheme bypasses or connects to, for the 2015 Base Year and three forecast years of 2025, 2040 and 2051.

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Table 4-5: AADT Vehicle Flows – Without-Scheme (Base Year 2015 and Forecast Years 2025, 2040 & 2051)

2025 2040 2051 Descriptio Section Direction 2015 Without- Without- Without- n Scheme Scheme Scheme

EB 17,900 20,500 21,700 22,200 A421, A West of WB 18,300 21,900 24,900 25,600 Black Cat Two-Way 36,200 42,400 46,600 47,800

NB 31,100 35,200 36,500 36,600 A1, North B of Black SB 29,800 34,500 37,100 37,700 Cat Two-Way 60,900 69,700 73,600 74,300

EB 14,400 17,100 18,100 18,200 A428, West of C WB 14,700 17,500 18,200 18,500 Barford Road Two-Way 29,100 34,600 36,300 36,700

EB 9,200 13,900 16,100 17,100 A428, East D of Barford WB 9,700 14,700 17,000 18,000 Road Two-Way 18,900 28,600 33,100 35,100

EB 11,400 13,300 14,900 15,400 A428, E West of WB 13,000 14,400 15,800 16,000 B1040 Two-Way 24,400 27,700 30,700 31,400

EB 11,800 13,600 15,200 15,600 A428, West of F WB 13,500 15,100 16,200 16,600 Caxton Gibbet Two-Way 25,300 28,700 31,400 32,200

EB 16,000 17,800 20,800 22,400 A428, East G of Caxton WB 17,800 19,400 21,000 22,500 Gibbet Two-Way 33,800 37,200 41,800 44,900

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Table 4-6 details the AADT forecast flows comparing the With-Scheme against the Without-Scheme scenarios, for all forecast years (2025, 2040 and 2051). This includes the two new sections of the Scheme route between Black Cat and Caxton Gibbet, Sections H and I.

Table 4-6: AADT Volumes Without and With-Scheme Scenarios (Forecast Years 2025, 2040 and 2051)

2025 2040 2051 Section Description Direction Without- With- Diff Diff Without- With- Diff Diff Without- With- Diff Diff Scheme Scheme (Vehs) (%) Scheme Scheme (Vehs) (%) Scheme Scheme (Vehs) (%)

EB 20,500 29,700 9,200 45% 21,700 38,000 16,300 75% 22,200 41,200 19,000 86% A421, West of WB 21,900 29,000 7,100 32% 24,900 40,100 15,200 61% 25,600 43,400 17,800 70% A Black Cat Two-Way 42,400 58,700 16,300 38% 46,600 78,100 31,500 68% 47,800 84,600 36,800 77%

NB 35,200 33,000 -2,200 -6% 36,500 37,800 1,300 4% 36,600 39,300 2,700 7% A1, North of Black SB 34,500 29,300 -5,200 -15% 37,100 36,200 -900 -2% 37,700 38,200 500 1% B Cat Two-Way 69,700 62,300 -7,400 -11% 73,600 74,000 400 1% 74,300 77,500 3,200 4%

EB 17,100 11,900 -5,200 -30% 18,100 13,900 -4,200 -23% 18,200 15,000 -3,200 -18% A428, West of WB 17,500 10,400 -7,100 -41% 18,200 12,600 -5,600 -31% 18,500 13,700 -4,800 -26% C Barford Road Two-Way 34,600 22,300 -12,300 -36% 36,300 26,500 -9,800 -27% 36,700 28,700 -8,000 -22%

EB 13,900 7,200 -6,700 -48% 16,100 9,300 -6,800 -42% 17,100 10,500 -6,600 -39% A428, East of WB 14,700 7,300 -7,400 -50% 17,000 9,900 -7,100 -42% 18,000 11,300 -6,700 -37% D Barford Road Two-Way 28,600 14,500 -14,100 -49% 33,100 19,200 -13,900 -42% 35,100 21,800 -13,300 -38%

E EB 13,300 600 -12,700 -95% 14,900 700 -14,200 -95% 15,400 800 -14,600 -95%

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2025 2040 2051 Section Description Direction Without- With- Diff Diff Without- With- Diff Diff Without- With- Diff Diff Scheme Scheme (Vehs) (%) Scheme Scheme (Vehs) (%) Scheme Scheme (Vehs) (%)

WB 14,400 600 -13,800 -96% 15,800 800 -15,000 -95% 16,000 1,000 -15,000 -94% A428, West of B1040 Two-Way 27,700 1,200 -26,500 -96% 30,700 1,500 -29,200 -95% 31,400 1,800 -29,600 -94%

EB 13,600 1,000 -12,600 -93% 15,200 1,100 -14,100 -93% 15,600 1,200 -14,400 -92% A428, West of F WB 15,100 900 -14,200 -94% 16,200 800 -15,400 -95% 16,600 800 -15,800 -95% Caxton Gibbet Two-Way 28,700 1,900 -26,800 -93% 31,400 1,900 -29,500 -94% 32,200 2,000 -30,200 -94%

EB 17,800 24,900 7,100 40% 20,800 31,300 10,500 50% 22,400 34,800 12,400 55% A428, East of G WB 19,400 26,300 6,900 36% 21,000 33,500 12,500 60% 22,500 37,200 14,700 65% Caxton Gibbet Two-Way 37,200 51,200 14,000 38% 41,800 64,800 23,000 55% 44,900 72,000 27,100 60%

EB - 15,400 - - - 21,300 - - - 23,700 - - New A428, Black H Cat to Cambridge WB - 16,500 - - - 24,100 - - - 26,800 - - Road junction Two-Way - 31,900 - - - 45,400 - - - 50,500 - -

EB - 23,000 - - - 29,900 - - - 32,200 - - New A428, Cambridge Road I WB - 25,000 - - - 33,900 - - - 37,200 - - junction to Caxton Gibbet Two-Way - 48,000 - - - 63,800 - - - 69,400 - -

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A summary of the impacts of the Scheme on the existing A428 with reference to the forecast daily flow changes is presented below. Section B, North of Black Cat to Wyboston a. In 2025, there is only a small reduction on the A1 between Black Cat and Wyboston. This is due to the improvement at Black Cat making the A1 more attractive; and the Scheme reducing rat-running traffic on local roads, such as Barford Road, between Tempsford and St Neots, with some of this traffic switching to the A1. b. In 2040 there is virtually no impact on traffic flows here. c. In 2051, there is a small increase of around 4% – reflecting the increased volume of traffic that is diverting from alternative minor roads given the increase in congestion at Black Cat in the 2040 and 2051 DM scenarios, compared to that in 2025. Sections C and D, west of Barford Road to Cambridge Road junction a. In 2025 there are more modest reductions in flows on the A428 west of Cambridge Road as these sections continue to be used by traffic accessing or egressing St Neots. b. In and after 2040 these reductions are proportionally slightly lower than in 2025, reflecting the increase in traffic from the proposed developments at Wintringham Park which occur after 2025. However, the reductions are still substantial, at around 50% of the Without-Scheme volumes. Sections E and F, Cambridge Road to Caxton Gibbet a. In 2025, the with-Scheme traffic volume changes are proportionally greatest on the existing A428 between Cambridge Road junction and Caxton Gibbet, respectively Sections E and F. These sections have forecasts reductions in traffic volumes of around 95% (between 26,000 and 27,000 vehicles per day, with residual flows of under 2,000 per day). b. The proportional changes in 2040 and 2051 are similar. Section A Western and Section G, Eastern End of the Scheme: a. In 2025 there are substantial increases in traffic flows (i.e. 38% west of Black Cat and east of Caxton Gibbet). b. In 2040 these increase further, amounting to 68% west of Black Cat and 55% east of Caxton Gibbet. c. In 2051 the increases amount to 77% west of Black Cat (Section A) and 60% east of Caxton Gibbet (Section G). Along the New Scheme route (Sections H and I): a. In 2025, there are forecast to be some 32,000 vehicles daily two-way on the western section west of the Cambridge Road junction and 48,000 on the eastern section east of the same junction.

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b. In 2040, there are forecast to be 45,400 vehicles (daily two-way flows) on the western section west of the Cambridge Road junction and 63,800 on the eastern section east of the same junction (35-40% higher than in 2025). c. In 2051, there are forecast to be 50,500 vehicles daily two-way on Section H west of the Cambridge Road junction and 69,400 on Section I east of the same junction (volumes around 5,000 higher than those in 2040). Traffic forecasts by time period for the Scheme link sections A-I for the core scenario are presented in Appendix E of the TFR, Appendix C to the ComMA. The full set of schematic AADT flow diagrams for the core scenario, are presented in Appendix D of the TFR, Appendix C to the ComMA. Additionally, the following are presented below (all in vehicles): a. Figure 4-3 – AADT for Base Year 2015. b. Figure 4-4 – AADT for 2040 DM. c. Figure 4-5 – Percentage change in AADT between the 2015 and 2040 DM. d. Figure 4-6 – AADT for 2040 DM and DS. e. Figure 4-7 – Change in AADT between the 2040 DM and DS. f. Figure 4-8 – Percentage change in AADT between the 2040 DM and DS. Figure 4-3 and Figure 4-4 respectively present the 2015 AADT flows and 2040 flows without the Scheme on roads in the vicinity of the A428. Figure 4-5 presents the forecast percentage increases in traffic between 2015 and 2040 without the Scheme. Figure 4-5 shows that the proportional flow increases between 2015 and 2040 tend to be much larger on minor roads compared to those on major roads. On east-west routes there are increases of 80-100% on the minor routes, compared to around 30% on the major routes. This reflects an increase in rat-running as traffic avoids the more congested A428. Figure 4-6 presents the forecast 2040 AADT two-way volumes across the Scheme area (for the With-Scheme scenario). This shows that there are forecast daily flows of 63,800 on the Scheme section east of the Cambridge Road junction and 45,350 west of this junction. West of Eltisley on the existing A428, daily two- way flows are forecast to reduce to 5,000 vehicles. The change and percentage change in AADT between the 2040 DM and DS as shown in Figure 4-7 and Figure 4-8. This demonstrates the impact of the Scheme on traffic flows across the area, with values in red indicating reductions in AADT. This clearly shows some benefits in terms of reduced traffic on the surrounding minor and secondary roads resulting from the Scheme.

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Figure 4-3: Annual Average Daily Traffic (AADT), 2015 Base Year (Vehicles)

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Figure 4-4: Annual Average Daily Traffic (AADT), 2040 Do Minimum (Vehicles)

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Figure 4-5: Comparison of 2015 to 2040 DM - Percentage Change in AADT

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Figure 4-6: Annual Average Daily Traffic (AADT), 2040 Do Something (Vehicles)

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Figure 4-7: Annual Average Daily Traffic (AADT), 2040 Do Something Less 2040 Do Minimum (Vehicles)

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Figure 4-8: Comparison of 2040 DM to 2040 DS - Percentage Change in AADT

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Journey Times One of the main objectives of the Scheme is to reduce congestion and journey times. As part of the A428 Strategic Traffic Model validation, several journey time routes were used to compare observed against modelled journey times. Some of these routes were used to compare the impacts of the Scheme on travel times. Figure 4-9 shows the four longer distance routes that have been used for this purpose and Figure 4-10 and Figure 4-11 show the local routes that have been assessed. The longer routes are the A421/A428 (Route 1), A1, A1198 and A603/B1042. Appendix G in the Traffic Forecasting Report presents the journey time data for all years for the Core scenarios.

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Table 4-7 shows how journey times are forecast to change along the longer distance routes between the Base Year and 2040 DM and DS scenarios, plus the A428. On the A421/A428 between 2015 and 2040, journey times are forecast to increase by up to 36% in the absence of the Scheme between Renhold junction and Caxton Gibbet, with the higher increases in the interpeak. Over the whole route between the M1 and M11 there is a forecast increase of around 20% between 2015 and 2040. On the A1 between Letchworth and Huntingdon the increase in journey time is forecast to be around 20-25% between 2015 and 2040. With the Scheme in place, journey times are forecast to reduce by about 50% along the A421/A428 between Renhold junction and Cambourne junction, from around 30 minutes to around 16 minutes at peak time in the peak direction in 2040. As the Scheme results in additional traffic to the west and east, the time saving from the M1 to the M11 is marginally less, at around 12 minutes at peak times. Along the A1, from Letchworth to the A1 (M) / A1307 junction, the Scheme results in travel time savings of between 1.5 and 3.5 minutes compared to the DM scenario in 2040. Table 4-8 additionally presents the forecast changes for selected local routes. The results for all local routes are also reproduced in Table 6-13 in the TFR (the Appendix C to the ComMA) for 2040, and in Appendix G of the TFR for all core scenarios. Of the local routes, there are also a number of reductions in journey times due to traffic re-routeing to the SRN roads. On Bedford Road between Renhold and Black Cat junctions, journey times reduce by 20-25% in the eastbound direction. On the route between St Neots and Papworth Everard via Toseland and Yelling, there are reductions of 10-15% in journey times in peak periods. There are also reductions on the minor roads between Renhold junction and Barford Road junction via Blunham and Tempsford.

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Table 4-7: Comparison of Journey Time Changes (Long Distance Routes)

2015 2040 BY DM Change Change DS Change Change Time Directio Distance Modelled DM Time DS Time Route Description Distance from BY from BY Distance from DM from DM Period n (km) (mm:ss) (mm:ss) (mm:ss) No. (km) (mm:ss) (%) (km) (mm:ss) (%)

EB 25.4 22:49 25.4 29:48 07:00 31% 25.2 15:34 -14:14 -48% AM WB 25.3 22:36 25.3 26:34 03:59 18% 25.5 15:08 -11:26 -43% A421/A428 (Renhold EB 25.4 19:30 25.4 26:26 06:55 36% 25.2 14:40 -11:46 -45% A428 junction to IP Cambourne WB 25.3 20:39 25.3 28:09 07:31 36% 25.5 15:51 -12:18 -44% junction) EB 25.4 22:38 25.4 26:17 03:39 16% 25.2 14:30 -11:47 -45% PM WB 25.3 23:57 25.3 30:41 06:44 28% 25.5 16:19 -14:23 -47%

EB 59.0 43:46 59.1 52:13 08:27 19% 58.9 40:27 -11:46 -23% AM WB 58.8 42:58 59.5 50:05 07:06 17% 59.7 40:38 -09:27 -19%

A421/A428 EB 59.0 39:42 59.1 47:48 08:07 20% 58.9 36:58 -10:50 -23% 1 (M1 J13 to IP M11 J14) WB 58.8 39:53 59.5 49:06 09:13 23% 59.7 38:24 -10:42 -22%

EB 59.0 44:56 59.1 51:55 06:58 16% 58.9 41:10 -10:45 -21% PM WB 58.8 43:42 59.5 52:04 08:22 19% 59.7 40:00 -12:04 -23%

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NB 51.9 32:38 51.9 40:20 07:42 24% 51.9 38:54 -01:26 -4% AM SB 51.3 36:52 51.2 46:15 09:23 25% 51.2 43:33 -02:41 -6% A1 NB 51.9 32:03 51.9 38:40 06:37 21% 51.9 38:02 -00:38 -2% (Letchworth to 2 IP A1307 SB 51.3 32:45 51.2 38:58 06:12 19% 51.2 35:26 -03:31 -9% junction) NB 51.9 35:56 51.9 45:09 09:13 26% 51.9 43:31 -01:38 -4% PM SB 51.3 33:35 51.2 39:53 06:18 19% 51.2 36:26 -03:27 -9%

EB 45.7 42:47 45.7 48:21 05:34 13% 45.7 45:18 -03:03 -6% AM WB 45.6 43:34 45.6 47:19 03:45 9% 45.6 46:23 -00:55 -2% A603/B1042 (Cardington EB 45.7 39:44 45.7 43:47 04:03 10% 45.7 42:22 -01:25 -3% 7 junction to IP M11 Junction WB 45.6 39:58 45.6 45:04 05:06 13% 45.6 43:15 -01:49 -4% 14) EB 45.7 42:20 45.7 45:00 02:40 6% 45.7 44:41 -00:19 -1% PM WB 45.6 42:18 45.6 49:40 07:22 17% 45.6 47:00 -02:40 -5%

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NB 31.4 25:24 31.3 26:46 01:22 5% 31.3 26:47 00:01 0% AM SB 31.4 28:07 31.2 34:38 06:31 23% 31.3 33:51 -00:46 -2% A1198 NB 31.4 24:42 31.3 26:42 02:00 8% 31.3 26:55 00:14 1% (Royston 8 IP A505/A1198 to SB 31.4 24:37 31.2 27:39 03:02 12% 31.3 27:28 -00:12 -1% A14 J24) NB 31.4 27:45 31.3 29:17 01:32 6% 31.3 29:55 00:38 2% PM SB 31.4 25:36 31.2 28:05 02:30 10% 31.3 28:14 00:09 1%

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Table 4-8: Comparison of Journey Time Changes (Local Routes)

2015 2040 BY DM Change Change DS Change Change Time Distance Modelled DM Time DS Time Route Description Direction Distance from BY from BY Distance from DM from DM Period (km) (mm:ss) (mm:ss) (mm:ss) No. (km) (mm:ss) (%) (km) (mm:ss) (%)

EB 7.5 04:19 7.5 08:35 04:16 99% 7.5 05:09 -03:26 -40% AM WB 7.5 04:12 7.5 04:12 00:00 0% 7.5 04:55 00:42 17% Bedford East EB 7.5 04:15 7.5 08:26 04:10 98% 7.5 04:58 -03:28 -41% 11a junction to IP Black Cat; WB 7.5 04:02 7.5 04:16 00:14 6% 7.5 05:08 00:53 21% via A421 EB 7.5 07:08 7.5 08:37 01:28 21% 7.5 05:00 -03:37 -42% PM WB 7.5 04:01 7.5 04:12 00:10 4% 7.5 05:08 00:56 22%

EB 7.9 07:31 7.9 09:10 01:39 22% 7.9 07:20 -01:49 -20% AM WB 7.7 07:02 7.7 07:26 00:24 6% 7.7 07:13 -00:13 -3% Bedford East EB 7.9 07:16 7.9 08:52 01:37 22% 7.9 07:16 -01:36 -18% junction to 11b IP Black Cat; WB 7.7 06:41 7.7 06:50 00:09 2% 7.7 06:50 00:00 0% via Great Barford EB 7.9 08:23 7.9 10:18 01:55 23% 7.9 07:44 -02:33 -25% PM WB 7.7 06:50 7.7 07:05 00:14 4% 7.7 07:03 -00:02 0%

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EB 21.5 21:02 21.7 23:12 02:10 10% 21.6 18:42 -04:31 -19% AM WB 21.5 19:07 22.2 20:51 01:45 9% 22.4 17:27 -03:25 -16% St Neots T.C. to EB 21.5 18:13 21.7 20:26 02:13 12% 21.6 16:55 -03:31 -17% 14a Madingley IP Mulch; WB 21.5 19:10 22.2 21:35 02:25 13% 22.4 17:53 -03:42 -17% via A428 EB 21.5 18:19 21.7 19:57 01:38 9% 21.6 16:43 -03:14 -16% PM WB 21.5 22:22 22.2 24:56 02:34 12% 22.4 19:24 -05:32 -22%

EB 30.7 29:08 30.7 30:15 01:07 4% 30.4 29:14 -01:02 -3% AM WB 30.7 29:48 30.7 30:26 00:39 2% 30.7 29:23 -01:03 -3% St Neots T.C. to EB 30.7 28:49 30.7 29:14 00:26 1% 30.4 28:52 -00:22 -1% 14b Madingley IP Mulch; WB 30.7 29:32 30.7 30:19 00:47 3% 30.7 29:08 -01:11 -4% via B1046 EB 30.7 28:59 30.7 29:28 00:29 2% 30.4 29:13 -00:15 -1% PM WB 30.7 30:13 30.7 32:57 02:44 9% 30.7 29:49 -03:08 -10%

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EB 17.2 17:38 17.2 22:14 04:36 26% 17.1 19:04 -03:10 -14% AM WB 17.2 19:51 17.2 22:07 02:16 11% 17.3 19:21 -02:47 -13% Bedford T.C. EB 17.2 17:21 17.2 21:42 04:22 25% 17.1 18:39 -03:03 -14% to Eaton 15a IP Socon; WB 17.2 17:47 17.2 22:22 04:36 26% 17.3 19:23 -03:00 -13% via A421 EB 17.2 20:31 17.2 22:11 01:41 8% 17.1 19:08 -03:03 -14% PM WB 17.2 18:35 17.2 22:32 03:57 21% 17.3 20:12 -02:19 -10%

EB 19.2 21:23 19.2 21:45 00:22 2% 19.2 21:31 -00:14 -1% AM Bedford T.C. WB 19.5 21:23 19.5 21:42 00:19 1% 19.5 21:28 -00:14 -1% to Eaton Socon; EB 19.2 21:13 19.2 21:29 00:15 1% 19.2 21:19 -00:09 -1% via B660, 15b IP Colmworth WB 19.5 21:17 19.5 21:39 00:22 2% 19.5 21:26 -00:13 -1% & Bushmead Roadon EB 19.2 20:53 19.2 21:17 00:24 2% 19.2 20:45 -00:32 -2% PM WB 19.5 21:34 19.5 22:06 00:32 2% 19.5 21:52 -00:15 -1%

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EB 11.5 14:47 11.5 16:35 01:48 12% 11.4 11:32 -05:03 -30% AM WB 11.5 13:19 11.5 14:46 01:27 11% 11.7 11:33 -03:13 -22% St Neots T.C. - EB 11.5 12:19 11.5 14:13 01:54 15% 11.4 10:44 -03:29 -25% Caxton 16a IP Gibbet; WB 11.5 13:22 11.5 15:19 01:57 15% 11.7 11:38 -03:41 -24% via B1428 & A428 EB 11.5 12:23 11.5 13:46 01:23 11% 11.4 10:34 -03:11 -23% PM WB 11.5 16:09 11.5 17:27 01:18 8% 11.7 12:18 -05:09 -30%

EB 13.6 16:00 13.6 16:33 00:33 3% 13.3 14:00 -02:33 -15% AM St Neots WB 13.6 14:06 13.6 14:43 00:38 4% 13.4 13:57 -00:47 -5% T.C. - Caxton EB 13.6 13:33 13.6 14:06 00:33 4% 13.3 13:30 -00:36 -4% 16b Gibbet; IP via B1043, WB 13.6 13:45 13.6 14:46 01:01 7% 13.4 13:53 -00:53 -6% Toseland & A1198 EB 13.6 14:00 13.6 14:20 00:20 2% 13.3 13:39 -00:41 -5% PM WB 13.6 14:33 13.6 16:08 01:35 11% 13.4 14:17 -01:52 -12%

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EB 12.1 08:27 12.1 13:12 04:45 56% 12.0 09:09 -04:03 -31% AM Bedford WB 12.0 10:19 12.0 12:42 02:23 23% 12.1 09:33 -03:08 -25% East junction to EB 12.1 08:11 12.1 12:38 04:27 54% 12.0 09:07 -03:32 -28% 17a Barford IP Roundabout WB 12.0 08:27 12.0 13:27 05:00 59% 12.1 09:50 -03:36 -27% ; via A421 & A428 EB 12.1 11:15 12.1 13:03 01:48 16% 12.0 09:25 -03:38 -28% PM WB 12.0 08:49 12.0 13:06 04:17 49% 12.1 09:50 -03:16 -25%

EB 15.2 15:26 15.2 16:23 00:57 6% 15.2 15:24 -00:59 -6% AM Bedford WB 15.1 15:43 15.1 16:51 01:08 7% 15.1 15:45 -01:06 -6% East junction to EB 15.2 15:22 15.2 15:56 00:34 4% 15.2 15:24 -00:33 -3% Barford 17b IP Roundabout WB 15.1 15:06 15.1 15:48 00:42 5% 15.1 15:30 -00:18 -2% ; via Gt Barford, & Tempsford EB 15.2 15:56 15.2 16:59 01:03 7% 15.2 15:38 -01:21 -8% PM WB 15.1 15:33 15.1 16:54 01:21 9% 15.1 15:54 -01:00 -6%

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Low and high growth scenarios Table 6-18 to Table 6-23 of the TFR, Appendix C to the ComMA, provide comparisons of AADT flows in 2025, 2040 and 2051 along the route for the Core, Low and High growth scenarios. The comparison of the Without-Scheme scenario shows little difference between Core, Low and High indicating that the existing A428 route between the A421, west of Black Cat and the A428, east of Caxton Gibbet is at capacity. For the With-Scheme scenario, it shows some greater differences between the growth scenarios as a consequence of the additional capacity that the Scheme provides. There are differences of around 3% to 4% in both scenarios compared to Core growth with Low growth flows being lower by this margin and High growth flows being higher. Table 6-24 to Table 6-29 of the TFR, Appendix C to the ComMA, report the journey time savings resulting from the Scheme, for all forecast years and Core, Low and High growth scenarios. The difference in journey times along the length of the Scheme between Renhold and Cambourne in 2040 is between about 0.5 and 1.25 minutes with lower time savings in the Low growth and higher time savings in the High growth scenario. On the A1 the time saving differences are up to 0.5 minutes with little difference on the other routes. For the majority of local routes in 2040, the time savings are lower in the Low growth scenario and higher in the High growth scenario with a maximum difference of about 1 minute on route 14 via the B1046. The full forecasting results of the Low and High growth scenarios, in terms of forecast traffic flows and journey times, are presented in the following locations within the TFR as attached in Appendix C of this report: a. Low & high growth scenario tables of Scheme link traffic forecasts by time period – Appendix I of TFR. b. Low & high growth scenario schematic link diagrams (AADT) – Appendix J of TFR. c. Low & high growth scenario schematic link diagrams (Average Hourly Flows) – Appendix K of TFR. d. Low & high growth scenario journey times – Appendix L of TFR.

4.6 Operational models In addition to the strategic modelling, a number of new, modified and existing junctions have also been selected for detailed assessment. These were grouped into 3 categories: a. New junctions forming part of the scheme. b. Existing junctions that are modified as part of the Scheme proposals and/or are in close proximity to the scheme. c. Existing junctions in the wider area that are affected due to flow changes as a result of the scheme.

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A full description of the development of the models of the new and modified junctions, together with the results, is included in the Transport Assessment (TA)23. A description of the development of the models to assess the existing junctions is provided in the Transport Assessment Annex (TAA)24. This report provides a summary of the development of the models. Junctions forming part of the Scheme Figure 4-12 illustrates the location of the new and modified junctions forming part of the Scheme proposals.

Contains Ordnance Survey Data © Crown Copyright and database right 2019 Figure 4-12: Locations of the Local Modelled Junctions within the TA

The junction capacity assessments have been undertaken utilising VISSIM and the TRL Junctions 9 software: ARCADY and PICADY. The most appropriate software was selected on the basis of scale and complexity of each of the junctions. VISSIM microsimulation modelling has been undertaken for the three main junctions of the Scheme. These are at: a. Black Cat (A1/A421-A428 junction). b. Cambridge Road (A428/B1428 Cambridge Road junction). c. Caxton Gibbet (A428/A1198 Ermine Street junction).

23 Transport Assessment (TA) - HE551495-ACM-GEN-GEN_SW_Z_ZZ-RP-DC-0001 24 Transport Assessment Annex (TAA) - HE551495-ACM-GEN-GEN_SW_Z_ZZ-RP-DC-0002

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VISSIM is a microscopic, behaviour-based simulation computer program developed to model both traffic and public transport. The program has many capabilities including modelling lane configuration, traffic composition and traffic signals. This makes it a very useful tool for more detailed operational assessment of transport schemes. The three vehicle compositions defined as part of the VISSIM modelling are: a. Cars. b. Light Goods Vehicles (LGVs). c. Heavy Goods Vehicles (HGVs). Bus services, pedestrians and cyclists were not coded in the network. Whilst these types of road user will be present at the junctions, their relatively small numbers are unlikely to affect the overall behaviour of motor vehicle traffic using them. The junctions have been assessed for the AM and PM peak hours, in the 2025 and 2040 future year scenarios. The traffic flows which have been input into VISSIM were extracted from the A428 Strategic Traffic Model core scenario, for all four modelled scenarios (2025 AM and PM, 2040 AM and PM). Traffic flows have been included for all movements at the junctions. The flows were extracted by cordoning the A428 Strategic Traffic Model to match the VISSIM-modelled area. As the A428 Strategic Traffic Model represents an average hour for each of the two peak periods, traffic data was uplifted to the 0700-0800 and 1700-1800 peak hours. The relevant uplift factors were: a. AM – 1.086. b. PM – 1.076. The results of the VISSIM modelling show that the three main junctions of the Scheme are predicted to operate within capacity and without any significant levels of congestion. The new dual carriageway sections have free-flowing traffic and merge/diverge movements are smooth. a. The average speed on the circulatory at Black Cat junction is between 20mph – 30mph for all modelled scenarios. The queues are short where traffic signals are present and there is sufficient capacity to accommodate them. There are no significant queues on most junction arms. Therefore, vehicles can merge and diverge from both the A1 and A421/A428 mainline carriageways without any difficulty. For the mainline carriageways the average speed of vehicles is above 60mph, indicating that traffic on the A1, A421 and A428 is free-flowing. In addition, there is no significant queueing modelled on the BP Garage service road.

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b. The average speeds at the Cambridge Road junction show that some modest queues may form on the roundabout approaches, but the queues do not extend between the roundabouts and should disperse quickly. There is also a slight reduction in speeds in the 2040 scenario, likely due to increased traffic volumes, but there is no significant congestion. The new dual carriageway operates well with the average speed above 60mph. c. The results for the Caxton Gibbet junction show that the traffic is free flowing in all scenarios (2025 AM, 2025 PM, 2040 AM and 2040 PM) with average speeds between 10mph and 30mph for all scenarios. There are some short queues on the approach arms to the north and south roundabouts, but these dissipate quickly. The new dual carriageway and on- slip and off-slip roads operate within capacity and are free-flowing. Models were also developed for five junctions that have new or modified layouts and/or are in close proximity to the Scheme: a. Bedford Road/ Roxton Road junction. b. Roxton Road roundabout. c. B1046/ Potton Road junction. d. A428/ Toseland Road/ Abbotsley Road junction. e. Eltisley link. The Junctions 9 ARCADY and PICADY modules, which are the industry standard software for modelling roundabouts and priority junctions respectively, have been used for the junction assessments to forecast capacity and delay. Version 9.5.1.7462 was used to develop all models. The junctions have been assessed for the AM and PM peak hours, 2025 and 2040 scenarios. Traffic flows input into Junctions 9 were extracted from the A428 Strategic Traffic Model, core scenario, for both 2025 and 2040. Similar to VISSIM modelling, the flows were extracted by cordoning the A428 Strategic Traffic Model to match the relevant area. The average peak period flows were converted to peak hour flows for the AM and PM using the factors 1.086 and 1.076 respectively. The results of the ARCADY and PICADY modelling indicate that the 5 junctions in close proximity to the Scheme are predicted to all operate well within capacity for the DS scenarios. A detailed description of the results of the assessment of these junctions is included in the Transport Assessment (TA). Other Non-Scheme Junction Assessments Wider area junction operational models were developed for a further 23 junctions over a wider area. The locations considered as part of this assessment are shown in blue in Figure 4-13. These junctions, selected on the basis of predicted flow changes as a result of the scheme, were considered to warrant further scrutiny.

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Contains Ordnance Survey Data © Crown Copyright and database right 2019 Figure 4-13: Locations of the Wide Area Modelled Junctions in the TAA

Table 4-9 summarises the types of modelling assessments undertaken in Cambridgeshire. The junction performance is summarised in Table 4-10 and the overall impacts are illustrated in Figure 4-14. The results provide a comparison between the DS and DM for the 2025 and 2040 forecast years. The results demonstrate that there will be significant increases in traffic flows on some arms at M11 Junction 14 Girton Interchange and M11 Junction 13 Madingley. There will be a modest increase in traffic flows at the A1 Buckden junction and on east-west routes through St Neots (Cambridge Street and Priory Hill Road). Apart from these, the overall results indicate that the other junctions will operate within capacity.

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Table 4-9: Summary of Modelling Undertaken for Cambridgeshire Junctions

Type of Assessment (including Model Software Application (Where Applicable)) Location Merge- Traffic ARCADY PICADY VISSIM Diverge Flows Analysis Analysis

A1 Buckden

roundabout

Yelling & Toseland Road & High Street crossroads

St Neots: east-west routes: Cambridge

Street and Priory Hill Road

Papworth Everard: three roundabouts on the A1198

Cambourne junction

Scotland Road,

Hardwick junction

Madingley Mulch

junction

M11 Junction 13

M11 Junction 14

eastbound merges

Wyboston

roundabout (*)

Barford Road

roundabout (*)

(*) – these junctions were also included in the Bedford Borough assessment, since they lie on the county boundary.

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Table 4-10: Summary of Junction Performance in Cambridgeshire

Junction Predicted Traffic Flow Impact Predicted Operational Impact

Small overall increase in traffic Slight increase in journey times/ A1 Buckden Junction flows delays

Some increases in 2025 East-west routes through particularly eastbound in the AM Not assessed, as predicted St Neots (Cambridge peak; a pattern of small changes in traffic flows in 2040 Street and Priory Hill increases and decreases in flow small Road)* by 2040

The introduction of the Scheme improves junction performance

Wyboston Roundabout** Overall reduction in traffic flows from overcapacity in DM on some approaches, predicted to operate within capacity in DS

The introduction of the Scheme improves junction performance Barford Road Overall reduction in traffic flows from overcapacity in DM on some Roundabout** approaches, predicted to operate within capacity in DS

Overall decrease in traffic flows Yelling- Toseland Junction remains within capacity with some increases in north- crossroads with minimal queues and delays south movements

Papworth Everard Not assessed, overall decrease in junctions (3 Overall decrease in traffic flows traffic flows roundabouts)

Overall increase in flows: some A428/Cambourne Junction remains within capacity significant increases on Junction with minimal queues and delays individual arms

Overall small increase in flows: A428/Scotland Road Junction remains within capacity some significant increases on Hardwick with minimal queues and delays individual arms

In isolation this junction remains A428/A1303 Madingley Some substantial increases in within capacity with low levels of Mulch Roundabout flow queuing and delays

Analysis of eastbound merge Significant increase in eastbound taper suggests that additional M11 J14 Girton flow along A428 offset to some capacity may potentially be Interchange extent by decreases on M11 and required at the A428/M11 A14 eastbound merge

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Junction Predicted Traffic Flow Impact Predicted Operational Impact

Significant increase in traffic Relatively minor increases in delay M11 J13 Madingley flows on some arms of the in 2025, becoming more junction significant by 2040

(*) An assessment of link flows, not junctions

(**) Junction also included in the Bedford Borough assessment, as it lies on the county boundary.

Contains Ordnance Survey Data © Crown Copyright and database right 2019 Figure 4-14: Summary of Impacts in Cambridgeshire Table 4-11 summarises the types of modelling assessments undertaken in Bedford Borough. The junction performance is summarised in

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Table 4-12 and the overall impacts are illustrated in Figure 4-15. The results provide a comparison between the DS and DM for the 2025 and 2040 forecast years. The results highlight that future capacity issues are predicted at the A421/A6 junction with small increases in traffic flow that will be made marginally worse by the Scheme. There will be minimal changes in traffic flows at the A421/A428 Marsh Leys junction, and an overall increase in flows at the A421/A4280 junction. There will be a reduction in traffic flows at the other junctions, which will all operate within capacity.

Table 4-11: Summary of Modelling Undertaken for Bedford Borough Junctions

Merge- Traffic Location ARCADY PICADY VISSIM Diverge Flows Analysis Analysis

Wyboston

roundabout (*)

Barford Road

roundabout (*)

A421/A4280

junction

A421/A603 junction

A421/A600

Shortstown junction

A421/A6 junction

A421/A428 Marsh

Leys junction

(*) – these junctions were also included in the Cambridgeshire assessment, since they lie on the county boundary.

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Table 4-12: Summary of Junction Performance in Bedford Borough

Predicted Traffic Junction Predicted Operational Impact Flow Impact

A421/A428 Marsh Leys Minimal changes in Not assessed as minimal changes in Junction traffic flows traffic flows

Small increases in Future capacity issues predicted, made A421/A6 Junction traffic flow marginally worse by Scheme

Overall reduction in Not assessed as overall reduction in A421/A600 Shortstown traffic flows traffic flow

Overall reduction in Not assessed as overall reduction in A421/A603 traffic flows traffic flows

By 2040, future capacity issues A421/A4280 Renhold Overall increase in predicted. However reassignment of Junction traffic flows traffic onto A421 results in shorter queues at the roundabouts in the DS

The introduction of the Scheme improves Overall reduction in junction performance from overcapacity Wyboston Roundabout* traffic flows in DM on some approaches, predicted to operate within capacity in DS

The introduction of the Scheme improves Overall reduction in junction performance from overcapacity Barford Road Roundabout* traffic flows in DM on some approaches, predicted to operate within capacity in DS

(*) Junction also included in the Cambridgeshire assessment, as it lies on the county boundary.

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Contains Ordnance Survey Data © Crown Copyright and database right 2019 Figure 4-15: Summary of Impacts in Bedford Borough

Table 4-13 summarises the types of modelling assessments undertaken in Central Bedfordshire. The junction performance is summarised in Table 4-14 and the overall impacts are illustrated in Figure 4-16. The results provide a comparison between the DS and DM for the 2025 and 2040 forecast years. There will be small overall changes in traffic flows at the 5 junctions in Central Bedfordshire with some relatively small increases in queues and delays as a result of the Scheme.

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Table 4-13: Summary of Modelling Undertaken for Central Bedfordshire Junctions

Merge- Traffic Location ARCADY PICADY VISSIM Diverge Flows Analysis Analysis

A1/A603

Roundabout, Sandy

Bedford Rd/High

Street, Sandy

A1 Biggleswade

North Roundabout

A1 Biggleswade

South Roundabout

A421/Beancroft

Road junction

M1 Junction 13

Table 4-14: Summary of Junction Performance in Central Bedfordshire

Predicted Traffic Flow Junction Predicted Operational Impact Impact

Small increases in traffic Relatively small increase in delays M1 Junction 13 flow overall

A mixed pattern of very Not assessed as overall small A421/Beancroft small increases and increases off set by small junction decreases in traffic flows decreases in traffic flows

Negligible change overall, A marginal increase in delay in with some increases in flow 2025 but with a more significant A1/A603 Sandy on the A1 and decreases reduction in delay in 2040 on the A603-B1042

Minimal change overall, Junction is significantly over Biggleswade North with increases in flow on capacity by 2025. However, the Roundabout the A1 and decreases on Scheme makes this only slightly the A6001-B658 worse

A mixed pattern of very Some relatively small increases in Biggleswade South small increases and queueing and delay, particularly on Roundabout decreases in traffic flows the A1 from the north

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Contains Ordnance Survey Data © Crown Copyright and database right 2019 Figure 4-16: Summary of Impacts in Central Bedfordshire

Full details of the development of the wider junction models together with the detailed results of the assessment are presented in the Transport Assessment Annex (TAA).

4.7 ComMA Data Requirements Table 4-15 summarises the relationship between the ComMA report and other ComMA Packages for information in Chapter 4, and identifies where further information can be found in relation to data used in the development of the forecast transport models.

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Table 4-15: ComMA Data Requirements Summary – Chapter 4

ComMA Reference to ComMA Package Requirement

The Appendix C of the ComMA, Stage 3 Transport Forecasting Package: Traffic Forecasting Report, January 2021. Specifically: Chapter 3 – Model Standards Chapter 4 – Forecast Assumptions Chapter 5 – Demand Forecasting – Reference Forecasts Forecast Chapter 6 – Strategic Model Forecast Results Assumptions Chapter 7 – Operational Assessment Appendix A – Uncertainty Log Tables Appendix B – Comparison of Unadjusted TEMPro to Adjusted Planning Data Appendix C – Scheme Plans

The Appendix C of the ComMA, Stage 3 Transport Forecasting Package: Traffic Forecasting Report, January 2021. Specifically: Chapter 5 – Demand Forecasting – Reference Forecasts Chapter 6 – Strategic Model Forecast Results Chapter 7 – Operational Assessment Chapter 8 – Construction Appendix D – AADT Flow Diagrams – Core Scenario Appendix E – Scheme Link Forecast Volumes by Time Period – Core Scenario Appendix F – Average Hourly Flow Diagrams – Core Scenario Appendix G – Journey Time Comparisons – Core Scenario Forecast Results Appendix H – Demand Model Convergence – Low Growth and High Growth Scenarios Appendix I – Scheme Link Forecast Volumes by Time Period – Low Growth and High Growth Scenarios Appendix J – AADT Flow Diagrams – Low Growth and High Growth Scenarios Appendix K – Average Hourly Flow Diagrams – Low Growth and High Growth Scenarios Appendix L – Journey Times – Low Growth and High Growth Scenarios Appendix M – Construction Scenario – 12-Hour Average Weekday Flow Diagrams Appendix N – Journey times

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5 Economic appraisal

5.1 Economic appraisal approach Introduction The economic appraisal of a highway scheme is an assessment of the net benefits to users and the wider community as a result of the proposed Scheme, set against the capital construction and operational and maintenance costs, incurred over a ‘whole life’ period. This section outlines the procedures and data used for the economic appraisal of the Scheme. This covers the derivation of monetary values for transport user benefits, accident benefits, environmental benefits and disbenefits in relation to greenhouse gases, local air quality, noise, wider economic impacts, journey time reliability benefits and scheme costs. The Economic Assessment described in this Chapter has been based on an opening year of 2025; this being the year assumed at the time of modelling when Scheme construction is expected to be completed (see the Transport Assessment Report [TR010044/APP/7.2]). However, since this report was prepared, Highways England has defined a reasonable worst case scenario construction programme, which assumes the ‘advanced works’ and the ‘enabling works’ being undertaken post grant of the A428 Order and may result in a 2026 opening year. This difference between the opening years does not invalidate the conclusions of the Economic Assessment as the forecast flows on the road network in years 2025 and 2040 are considered to be reasonably representative of the traffic flows that would exist on the network in year 2026 and 2041 respectively. Scope of appraisal The economic appraisal of the Scheme has been prepared in accordance with the Green Book - Appraisal and Evaluation in Central Government, 2018 edition25 (“the Green Book”). The economic appraisal comprised four components: a. Economic benefits to road users, including time savings and vehicle operating costs. b. Economic disbenefits to road users associated with the delays during the construction of the Scheme. c. Accident savings and associated economic benefits. d. Monetised environmental benefits and disbenefits from changes to greenhouse gas emissions, local air quality and noise.

25 This was the current version at the time of the appraisal.

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The benefits from these four categories were combined and compared to costs to produce an initial Benefit to Cost Ratio (BCR), as reported in Section 5.4 of the ComMA. (A full description is provided in Section 4.6 of the Economic Assessment Report (EAR), Appendix D to the ComMA). The following additional assessments were carried out and were included in the adjusted BCR: a. Wider economic impacts resulting from the Scheme. This was carried out using the DfT’s Wider Impacts in Transport Appraisal (WITA) program which follows the principles and formula set out in the TAG Unit A2.1 guidance b. Journey time reliability benefits. This comprised economic benefits as a result of more reliable journey times. The two additional assessments provided the basis for deriving an adjusted BCR, which is reported in Section 5.4 (and in more detail in Section 4.8 of the EAR, Appendix D to the ComMA). Department for transport ‘route map’ In July 2020 the Department for Transport published ‘A route map for updating Transport Analysis Guidance (TAG) during uncertain times’. This was a response to the unexpected events which have occurred in 2020, including the COVID-19 pandemic and the changes to the economic and fiscal outlook that could have a considerable bearing on scheme appraisals. The route map sets out how the appraisal framework should take account of these future trends in relation to the methods used within TAG. It is expected that revised TAG guidance will be issued in Spring 2021 with subsequent updates issued as and when issues are addressed. The route map advises that the impact of the new OBR economic growth forecasts and high carbon values should be assessed through the use of sensitivity testing prior to the release of changes to TAG guidance in 2021. The forecasts and economic appraisal for the Scheme presented within this Chapter, were completed prior to the publication of the DfT route map. However, a sensitivity test using the interim carbon values was subsequently undertaken and the results are presented within this report. It is intended that, in accordance with the advice issued in the DfT route map, a sensitivity test will be prepared to assess the impact of the revised economic growth forecasts on the economic benefits of the Scheme.

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The economic growth sensitivity test would involve re-modelling and re- forecasting. The first stage is anticipated to involve testing the sensitivity of future demand in response to the revised forecasts of economic growth. This would be carried out by running the variable demand model using the revised TAG data book. The second stage is anticipated to involve assessing the sensitivity of the economic benefits. This would utilise the revised demand flows in stage 1 to derive estimates of user benefits from TUBA, COBALT and WITA based upon the revised TAG parameters. It is anticipated that this work will be reported as soon as practically possible following acceptance of the DCO application. Further details of our approach to dealing with the uncertainty arising from COVID-19 and the resultant changes to the economic outlook is described in more detail in ‘Strategy for Dealing with Uncertain Outcomes Arising from COVID-19’ (TR010044/APP/7.11). Economic assessment overview The costs of the Scheme comprise: a. The Scheme capital costs. b. The additional operating costs of the new road and junctions. c. The net difference between the Without-Scheme and With-Scheme forecast future maintenance capital costs. The benefits of the Scheme were calculated from a number of sources, all of which took inputs from the SATURN assignment models: a. Transport Economic Efficiency (TEE) benefits (savings relating to travel times, vehicle operating costs, indirect tax revenues and user charges) obtained using the DfT’s Transport Users Benefit Appraisal (TUBA) program. b. Delay costs to users during construction, also obtained using TUBA. c. Accident (Collision) benefits, forecast using the DfT’s Cost and Benefit to Accidents – ‘Light Touch’ (CoBALT) program. d. Reliability benefits, forecast using a bespoke methodology, as opposed to using the Motorway Reliability Incidents and Delays (MyRIAD) software, which was unsuitable for single carriageway upgrades to dual carriageway at the time this work was undertaken. e. Wider economic impacts, obtained using WITA. In addition, a monetised estimate of greenhouse gas impacts was calculated using the Emissions Factor Toolkit (EFT, Version 9) and the Greenhouse Gases workbook. Noise and Air Quality impacts were also similarly appraised. Delays during maintenance periods were not considered as part of this appraisal, but would be expected to be lower for the With-Scheme scenario compared to the Without-Scheme scenario. The results from the different elements of the economic assessment are presented in three summary tables:

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a. The Transport Economic Efficiency (TEE) Table, as Table 5-5. b. The Public Accounts (PA) Table, as Table 5-4. c. The Analysis of Monetised Costs and Benefits (AMCB) Table. The full AMCB table is presented in Appendix D of the EAR, Appendix D to the ComMA. An aggregated version is also given in Table 5-18. The economic assessment was undertaken for the Core Scenario (central growth) together with two sensitivity tests: a. A Low growth sensitivity test. b. A High growth sensitivity test. The Distributional Impact Analysis (DIA) based on the Scheme benefits is reported in the Stage 3 Distributional Impacts Report, which is included as a separate part of the Economic Appraisal Package, Appendix E to the ComMA. The Appraisal Summary Table (AST) and supporting worksheets report is also included as a separate part of the Economic Appraisal Package, Appendix F to the ComMA. Annualisation Annualisation factors are required so that the benefits from each distinct modelled time period could be expanded to represent the full appraisal period across the whole year. The economic assessment takes account of the benefits accruing on both weekdays and at weekends (Table 5-1). The Scheme will also produce benefits in the weekday off-peak period and during the weekend. Traffic models for the weekday off-peak period were available whereas weekend models were not. Using observed traffic data, the number of hours during the weekend that were equivalent to weekday interpeak traffic volumes were determined. Weekday interpeak trip matrices were adjusted to account for different vehicle and purpose splits between the two periods and input to TUBA in conjunction with interpeak travel time and distance matrices. Annualisation factors for the weekday models were based on the model being representative of an annual average weekday. The annualisation factor for each TUBA time period must also incorporate the number of times the period occurs per year, with the year divided up as follows: a. 253 normal weekdays. b. 52 weekends. c. 8 Bank Holidays The annualisation factors are shown in Table 5-1. This results in most hours of the year being accounted for with the exception of 1860 weekend hours when volumes are less than those in weekday inter-peak hours.

Table 5-1: Annualisation Factors for AM, IP, PM and OP

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Model Period Days Factor Hours

AM 3 253 759

IP 6 253 1518

PM 3 253 759

OP 12 253 3036

Weekend & Bank Holidays 112 828

Price base and discount year The economic modelling used a 2010 price base year and this is also the year to which costs and benefits were discounted. Masking of user benefits The TUBA road user benefits, including the user journey time and operating costs, were assessed over the whole of the model area although some masking of these benefits was undertaken where unintuitive outcomes were obtained. The masking process was applied at a sector level whereby the 973 traffic zones within the model were appended to one of 21 sectors as shown in Figure 5-1. Sector 21 was formed of 7 traffic zones that were excluded to avoid unexpected benefit changes that were noted to occur between the three growth scenarios modelled.

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The masking matrix applied is shown in Figure 2-3 of the EAR, Appendix D to the ComMA. Table 5-2 shows the impact of masking on the Present Value Benefits (PVBs).

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Table 5-2: Comparison of the Impacts of the Masking Tests on Present Value Benefits (PVBs) – All Time Periods

Core Low High

PVB (£000's) ALL Periods 674,334 617,892 864,513

No Masking Difference from Core -56,442 190,180

Proportion of Core 91.6% 128.2%

PVB (£000's) ALL Periods 672,485 612,198 759,976

Mask V5b Change from Non-Masked -1,849 -5,693 -104,537

21 Sector Difference from Masked Core -60,287 87,491

Proportion of Masked Core -0.3% 91.0% 113.0%

5.2 Scheme costs Construction costs Scheme construction costs were provided by Highways England’s Commercial Services Division (HECSD) in May 2019. The cost estimate was based on a Regional Delivery Partnership (RDP) procurement route, with an expected outturn cost of £812.5 million (2019 Quarter 1 price base), including Portfolio risk. The costs were provided in the standard HECSD format that is compatible with input to the TUBA program. This is provided in Appendix A of the EAR, Appendix D to the ComMA. The expenditure profiles were based upon cost estimates for each financial year prepared at a base date and then inflated to outturn costs using Highways England’s projected construction related inflation. These costs were then rebased to 2010 calendar year profiles for economic calculations, using the Gross Domestic Product (GDP) deflator series as published in the TAG Databook. Table 3-1 in the EAR (Appendix D to the ComMA) provides a breakdown of the construction costs in undiscounted 2010 ‘factor’ prices, and Table 3-2 in the EAR provides the breakdown of the corresponding ‘market prices’ (discounted to 2010). In summary: a. The total undiscounted construction cost in undiscounted 2010 ‘factor’ prices is £562.1 million. b. The present value of investment costs in discounted 2010 ‘market’ prices is £435.6 million.

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Operating and maintenance costs Operating and Maintenance (O&M) costs were provided by HECSD in July 2020. In addition to the O&M costs for the new dual carriageway, O&M costs for the existing section of the A428 to be de-trunked were also included in the With- Scheme estimate, but with an allowance for the reduction in traffic flow forecast on that section. The expenditure profile was based upon the O&M cost estimates prepared in 2019 Q1 prices and then inflated to outturn costs using Highways England’s projected construction related inflation. This gave a net outturn O&M cost of £380.5 million. The outturn costs were then rebased to 2010 calendar year profiles for economic calculations, using the GDP-deflator series as published in the TAG Databook. The O&M costs are presented in Table 5-3.

Table 5-3: Operating and Maintenance Costs (2010 Undiscounted Factor Prices)

Operating Costs Maintenance Costs Total O&M Costs

(£000’s) (£000’s) (£000’s)

Without Scheme 8,203 53,688 61,892

With Scheme 41,685 139,958 181,643

Net Scheme 33,482 86,270 119,751 Costs

After converting from 2010 Factor to Market prices and discounting to 2010, the operating and maintenance costs total £18.78 million without the Scheme, £46.33 million with the Scheme and result in a net Stage 3 operating and maintenance cost of £27.6 million. The yearly operating and maintenance costs in 2010 discounted market prices are shown in Figure 3-2 and in Table 3-4 in the EAR, Appendix D to the ComMA. Public Accounts (PA) Table and Present Value of Costs (PVC) The full PA table is presented in Appendix C of the EAR (Appendix D to the ComMA) and a condensed version is given in Table 5-4. This shows the discounted value of the operating and maintenance costs as £27.6 and the investment cost of the Scheme as £435.6 million giving a total PVC of £463.2 million. The Scheme increases indirect tax revenues accruing to government by £83.8 million.

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Table 5-4: Condensed Public Accounts Table (£000s Discounted and Deflated to 2010)

Public Accounts Costs

Central Government Funding (Transport)

Operating costs 27,550

Investment costs 435,603

Present Value of Costs (PVC) 463,153

Central Government Funding (Non-Transport)

Indirect Tax Revenues (Operation) -83,919

Indirect Tax Revenues (Construction) 142

Wider Public Finances -83,777

5.3 Scheme benefits Operation transport economic efficiency The Transport Economic Efficiency (TEE) benefits consist of travel time benefits, Vehicle Operating Costs (VOCs) and indirect tax revenue changes as a result of the Scheme. The DfT program Transport User Benefits Appraisal (TUBA) v1.9.13 was used to assess the benefits arising from changes in journey times, vehicle operating costs and indirect tax revenues, which are calculated separately for Business Users and Consumer Users. TUBA calculates benefits for the modelled years; 2025, 2040 and 2051 which are inputs to the software. Beyond 2051 there is assumed to be no change in trips or travel time and distance. Benefits for the intermediate years are interpolated, with benefits beyond 2051 extrapolated up to the 60-year horizon year 2084 and adjusted using forecast changes to values of time. The benefits for the individual years are then discounted to 2010 over the full 60-year appraisal period to compare costs and benefits. Standard values of time, operating costs and other related economic parameters for traffic appraisal are applied to the calculation of road user costs, based on the standard ‘economic parameter file’ available from the DfT TUBA website, based on the May 2019 TAG Databook. In accordance with TAG guidance, an adjustment was made so that 12% of LGV trips were classed as ‘other’, while the remaining 88% were classed as business trips. A copy of the economic parameter file is in Appendix B of the EAR, Appendix D to the ComMA. As detailed in Section 2.5 of the EAR (Appendix D to the ComMA), TUBA outputs were masked at a sector level. The benefits calculated by TUBA presented in this report are based on the masked outputs.

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The Transport Economic Efficiency (TEE) user costs and benefits by road user, calculated by TUBA, are presented in Table 5-5.

Table 5-5: Transport Economic Efficiency Benefits (£000s Discounted and Deflated to 2010)

VOC Total Indirect User VOC Total Road User (Non- User Tax Total Time (Fuel) VOC Fuel) Benefits Revenue

Consumer User

Commuting 141,956 589 -18,346 -17,757 124,199 9,968 134,167

Other 311,952 -1,409 -108,748 -110,157 201,794 62,899 264,693

Net Consumer 453,908 -821 -127,094 -127,914 325,993 72,867 398,860

Business User

Personal 120,790 459 5,274 5,732 126,523 7,176 133,699

Freight 136,973 -6,946 6,023 -923 136,050 3,876 139,926

Net Business 257,763 -6,487 11,297 4,810 262,573 11,053 273,625

Present Value of Transport Economic 711,670 -7,308 -115,797 -123,105 588,566 83,919 672,485 Efficiency Benefits (PVB)

Figure 5-2 presents the road user benefits for each year of the economic appraisal period, in terms of 2010 prices, discounted to 2010. This shows that the Scheme benefits increase each year from 2025, but that the rate of increase reduces from 2040 onwards. The decline post-2051 is due to discounting, as undiscounted benefits are constant after 2051.

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Figure 5-2: Profile of Benefits 2025 to 2084 (£000s Discounted and Deflated to 2010)

Table 5-6 shows a breakdown of the discounted road user benefits from TUBA for each time period. This shows that the interpeak accounts for about 35% of the total benefits, the AM and PM peak periods both contribute 20% with the Off- Peak and Weekend accounting for 8% and 18% respectively. Table 5-6 also shows that benefits per hour are higher in the AM and PM peak periods than in the interpeak; this is due to lower congestion levels in the interpeak.

Table 5-6: TEE Benefits by Time Period (£000s Discounted and Deflated to 2010)

VOC Total Indirect Benefits Total Time Period User Time VOC (Fuel) (Non- User Tax Total per VOC Fuel) Benefits Revenue Hour

AM peak 138,365 46 -19,104 -19,058 119,307 14,392 133,700 176

PM peak 142,499 1,163 -19,732 -18,569 123,931 13,058 136,989 180

Interpeak 241,721 -3,048 -32,886 -35,934 205,787 26,836 232,623 153

Off-Peak 60,513 -5,301 -15,971 -21,272 39,242 12,234 51,476 17

Weekend 128,571 -168 -28,105 -28,272 100,299 17,399 117,697 142

Total 711,670 -7,308 -115,797 -123,105 588,566 83,919 672,485 n/a

Table 5-7 shows the benefits for each time period by user class. Car Commute accrues the most benefits in the PM peak period. Car Other accrues the highest benefits across the remaining periods.

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Table 5-7: Benefits by User Class and Time Period (£000s Discounted and Deflated to 2010)

User Class AM PM Interpeak Off Peak Weekend Total

Car Business 31,610 24,771 55,570 9,249 12,498 133,699

Car Commute 28,901 46,444 28,697 14,217 15,908 134,167

Car Other 34,371 38,604 84,559 24,417 78,419 260,370

LGV 19,743 16,977 31,306 3,099 7,329 78,454

HGV 19,075 10,192 32,492 493 3,544 65,796

Total 133,700 136,989 232,623 51,476 117,697 672,485

Table 5-8 shows the journey time benefits and vehicle operating costs broken down by time saved per trip, and Table 5-9 shows these benefits split by trip distance. Indirect tax revenue is not included in Table 5-8 and Table 5-9.

Table 5-8: Journey Time Benefits and Vehicle Operating Costs by Trip Time Variation (£000s Discounted and Deflated to 2010)

Amount of Time Saved Purpose < -5 -5 to -2 -2 to 0 0 to 2 2 to 5 >5 Total mins mins mins mins mins mins

Business 150 -4,706 -60,520 100,593 92,277 134,778 262,572

Commutin -178 -3,015 -57,399 64,486 62,341 57,963 124,198 g

Other 294 -2,512 -64,845 90,562 87,596 90,699 201,794

Total 266 -10,233 -182,764 255,641 242,214 283,440 588,564

Table 5-8 above also shows a higher proportion of benefits accrued for business trips with a time saving of over 5 minutes. For commuting and other trips, time savings are similar across the three ranges. The disbenefits occur mainly due to time increases of less than two minutes, which suggests that for journeys which experience an increase in journey time due to the Scheme, the increase is minimal with only a very small proportion experiencing an increase of more than five minutes. The total benefits are fairly evenly split across the 0 to 2, 2 to 5 and >5 minutes time saving segments. Table 5-9 shows the largest proportion of benefits by distance are for trips between 50kms and 100kms, with trips 25kms to 50kms the next largest segment.

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Long-distance trip benefits are largest for business users and lowest for commuting.

Table 5-9: Journey Time Benefits and Vehicle Operating Costs by Distance Travelled (£000s Discounted and Deflated to 2010)

Trip Distance

Purpose Total

kms kms kms kms kms kms

>200 >200

1 to 5 to 5 1

100 to 100

5 to 10 to 10 5

< 1 kms <1 to 25 10 to 50 25

200 kms 200 50 to 100 to 100 50

Business -64 -18 -949 12,597 55,433 100,935 72,246 22,390 262,570

Commuting -160 -2,621 -4,547 13,664 59,634 49,552 7,864 813 124,199

Other -548 -660 -4,719 35,039 69,829 73,989 24,322 4,542 201,794

Total -772 -3,299 -10,215 61,300 184,896 224,476 104,432 27,745 588,563

The spatial distribution of the journey time benefits and Vehicle Operating Costs (VOCs) resulting from the Scheme are presented in Figure 5-3 in terms of percentage of total benefits by sector origin. The largest proportion of the total benefits are for the sectors either end of the new dual carriageway; Bedford and Milton Keynes & Central Beds to the west and East of A1198 and Cambridge to the east. St Neots also has a higher proportion of the benefits due to the Cambridge Road junction. The largest individual sector-sector user benefits are for trips between Milton Keynes / Bedford / St Neots and East of A1198/ Cambridge. The benefits to north-south traffic due to the reduced congestion at Black Cat are also evident by the higher proportion of benefits in the sectors to the north and south such as Peterborough and London & Hertfordshire compared to the sectors west of Milton Keynes and east of Cambridge.

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Figure 5-3: Percentage of Total Journey Time / VOC benefits by Sector Origin

Overall, the Scheme provides benefits of approximately £589 million to transport users across the 60-year appraisal period (£m discounted and deflated to 2010). Accidents An assessment of the benefits from accident savings was undertaken using the Department for Transport’s (DfT) Cost and Benefit to Accidents – Light Touch (CoBALT) program. Separate Link and Junction assessments were run in CoBALT for the existing A428 and the Scheme, with a combined link and junction assessment used for the remainder of the network. CoBALT calculates the number of accidents on each link in each year of the evaluation period using Average Annual Daily Traffic (AADT) flows, link lengths and accident rates per million vehicle kms. The results of the CoBALT analysis in terms of predicted accident and casualty savings as a result of the Scheme, are presented in Table 5-10.

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Table 5-10: Accident Savings Over the 60-year Evaluation Period

Number of Number of Casualties (60 Scenario Accidents Years) (Total 60 years) Fatal Serious Slight

Do Minimum 40,006 911 6,615 50,113

Do Something 39,406 904 6,499 49,308

Change 600 8 116 805

Table 5-10 above shows that the total number of accidents saved by the Scheme is forecast to be 600 over the 60-year assessment period. This saving consists of eight fatal, 116 serious and 805 slight casualties, as each accident can have more than one casualty. The economic value of the accident savings is presented in Table 5-11, with the benefits totalling £29.5 million in discounted 2010 prices.

Table 5-11: Present Value of Accident Benefits (£000s Discounted and Deflated to 2010)

Scheme Without Scheme With Scheme Benefits

Accident Costs (£000’s) 2,067,811 2,038,283 29,528

Monetised Environmental Benefits Guidance in TAG Unit A3 Environmental Impact Appraisal was followed to assess the impacts of the Scheme on local air quality, noise and greenhouse gases. It is predicted there would be an increase of 3,313,499 tonnes in emissions of carbon dioxide (CO2) associated with the affected road network over the 60-year appraisal period. This equates to a present value of -£127.0 million in discounted 2010 prices. It should be noted that the greenhouse gas emissions figures may be overestimated due to differences in the vehicle fleet mix between Road Traffic Forecasts (RTF) 2018 and the Emissions Factor Toolkit (EFT) v9. This is because the data in the EFT v9 stops at 2030 and therefore does not include the increased proportion of electric vehicles forecast in RTF 2018. The analysis indicates that there is a reduction in local ambient air quality with respect to Nitrogen Dioxide (NO2) but an improvement in Particulate Matter 10 (PM10) emissions. Overall, a net detrimental change is predicted as a result of the Scheme.

For Particulate Matter 2.5 (PM2.5) there is a beneficial change in concentration, but a worsening from other impacts. Overall there is a net beneficial change as a result of the Scheme. For NO2 there is a beneficial change in concentration, but a

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worsening from other impacts; and overall there is a net detrimental change as a result of the Scheme. This equates to a present value of -£0.8 million in discounted 2010 prices. Noise increases are predicted at receptors near to the proposed alignment and around existing roads where vehicle numbers increase as a result of the proposed Scheme. However, the impact of this is small and outweighed by noise decreases predicted at a small number of receptors during the night. The overall present value is £2.2 million in discounted 2010 prices. The environmental impacts that are included in the initial and adjusted BCR are summarised in Table 5-12.

Table 5-12: Summary of Environmental Impacts (£000s Discounted and Deflated to 2010)

Benefits

Carbon Benefits (Greenhouse Gas) -127,043

Monetised Noise Benefits 2,157

Monetised Air Quality Benefits -777

Construction-Related Delays The impacts to transport users caused by traffic management measures during the construction of the Scheme were assessed using a series of fixed demand assignments to bespoke networks reflecting the various phases of construction. The results of these assignments were compared against the 2025 Do Minimum network. As noted in section 5.1 above, the assessment was based upon the assumption that the main construction works would commence in Spring 2022 and be completed in Spring 2025, with some preliminary works in the Black Cat area commencing around six months ahead of the main construction works. Based on the available information, it was determined that there would be four construction phases and each of these were modelled by adapting the 2025 Do Minimum model. The resultant construction-related user disbenefits have been summarised in Table 5-13 by construction phase, and Table 5-14 by road user. There is a total disbenefit of £34.9 million in discounted 2010 prices due to construction delay impacts.

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Table 5-13: Scheme Construction – Benefits by Construction Phase (£000s Discounted and Deflated to 2010)

VOC Total Indirect Construction User VOC Total (Non- User Tax Total Phase Time (Fuel) VOC Fuel) Benefits Revenue

1 -3,121 90 -96 -6 -3,127 -50 -3,176

2 -12,832 279 -321 -42 -12,874 -153 -13,027

3 -9,536 -48 -450 -498 -10,034 30 -10,004

4 -8,259 -51 -396 -447 -8,706 31 -8,675

Total -33,748 271 -1,263 -993 -34,740 -142 -34,883

Table 5-14: Scheme Construction – Benefits by Road User (£000s Discounted and Deflated to 2010)

VOC Total Indirect User VOC Total Road User (Non- User Tax Total Time (Fuel) VOC Fuel) Benefits Revenue

Consumer User

Benefits

Commuting -8,365 -47 8 -40 -8,405 28 -8,376

Other -13,704 -126 -206 -332 -14,036 75 -13,961

Net Consumer Benefits -22,069 -173 -198 -371 -22,441 104 -22,337

Business User Benefits

Personal -4,977 -65 -433 -498 -5,475 37 -5,438

Freight -6,702 509 -632 -123 -6,825 -283 -7,108

Net Business Impact -11,678 444 -1,065 -621 -12,300 -246 -12,546

Present Value of Transport Economic -33,748 271 -1,263 -993 -34,740 -142 -34,883 Efficiency Benefits (PVB)

Wider Economic Impacts Wider economic impacts refer to economic impacts which are additional to transport user benefits. They arise because market failures in secondary markets (non-transport markets), such as the product, labour and land markets, mean that the full welfare impact of a transport investment may not be reflected in the transport market.

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An assessment of the wider economic impacts of the Scheme, which are supplementary to the conventional transport user benefits, was undertaken in line with the TAG A2 series of Units. The wider economic impacts are described in TAG Unit A2 and can be divided into three distinct groups on the basis of land use change; fixed land use, implicit land use change and explicit land use change. This determines within which level of analysis they are included and how these impacts are reported within the economic assessment.

Table 5-15: Relationships between Wider Economic Impacts, Level of Analysis and Land Use Assumptions

Level 3 (Indicative Level 1 Level 2 (Adjusted Monetised Impacts

(Initial BCR) BCR) or Non-Monetised Impacts)

User Benefits Fixed Land Use Static Clustering

Output Change in imperfectly

Competitive Implicit Land Markets Use Change Labour Supply

Impacts

Dependent

Development

Move to More/Less

Explicit Land Productive Jobs Use Change Dynamic Clustering

Supplementary

Economic Modelling

*Note that the arrows signify the previous levels of analysis that are required

Source: TAG Unit A2-1, Table 2 For this analysis, Level 2 impacts were assessed based on fixed land use outputs from the transport model. This was considered a proportionate approach in line with TAG Unit A2-1. The benefits associated with the wider economic impacts were calculated using the DfT’s ‘Wider Impacts in Transport Appraisal’ (WITA) program, which follows the principles and formulae set out in the TAG Unit A2.1 guidance. The WITA assessment was based on the AM, interpeak and PM only as the vast majority of

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business-related trips (commute and employers’ business) occur in those periods. The following components were assessed: a. Agglomeration benefits (referred to as Static Clustering) – These arise from benefits arising relating to economic density and business productivity. When employment clusters together, the jobs in the cluster are likely to be more productive than they otherwise would be, due to better access to labour, increased competition between suppliers and greater interaction between businesses spreading knowledge. The Scheme promotes increased agglomeration leading to a benefit of £230.5 million across the appraisal period. b. Increased output in imperfectly competitive markets – In markets which are dominated by a few suppliers, prices may be above the quantity which would occur in competitive markets. Transport investment may lead to a price reduction and an increase in the quantity supplied, through its impact upon firms’ cost base. By improving journey times between these two areas, the Scheme will enable easier, and cheaper, travel for long distance business and freight trips – providing benefits in the output of goods that use transport. This benefit is calculated as 10% of the benefits to business users, which are extracted from the TUBA appraisal; in this case, a benefit of £26.3 million. c. Labour supply impact –The guidance for this wider economic impact is given in TAG Unit A2.3. This wider economic impact generates benefits resulting from calculated changes in national employment (paragraph 3.1.2 of the Unit). As such – if it is included – data from the full model network/matrix should be included in the calculations (otherwise displacement of jobs from external areas to internal areas might be missed). The calculations (performed within WITA) use the change in generalised cost for a commuting round trip to calculate the change in employment, the resulting increment in GDP and the resulting increase in taxation paid. In this case, the Scheme is estimated to have a positive impact on the potential labour supply for businesses in the area of £2.0 million. The results of the DfT’s ‘Wider Impacts in Transport Appraisal’ (WITA) analysis are presented in Table 5-16 and show that wider economic impacts provide total benefits of £258.7 million.

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Table 5-16: Results of WITA Analysis (£000s Discounted and Deflated to 2010)

Wider economic Category benefits

Agglomeration - Manufacturing 8,592

Agglomeration - Construction 11,269

Agglomeration - Consumer Services 47,622

Agglomeration - Producer Services 162,973

Agglomeration - Total 230,456

Increased output in imperfectly competitive 26,257 markets

Labour supply impact 1,960

Total 258,673

Journey Time Reliability In accordance with TAG, the measure of journey time variability employed was the standard deviation of journey times. The monetary benefits of improved reliability were calculated by applying TAG values of time (as adjusted by the reliability ratio) to the change in standard deviation of the journey times. A single carriageway version of MyRIAD was not available at the time of analysis. Existing guidance26 provides a methodology for calculating reliability benefits for ‘Urban roads’, ‘Inter urban motorways and dual carriageways’, but was not suitable for assessing an improvement to a rural single carriageway, while the methodology provided for ‘Other roads’ did not provide a mechanism for monetising benefits. The methodology therefore adopted for the Scheme is similar to the accepted methodology applied to the A303 Amesbury to Berwick Down improvement scheme (which is also a Highways England improvement from rural single to dual carriageway). The approach taken was to analyse current observed Trafficmaster data; cluster data by day of week/time of day/season; and then compare the variability on an existing section of dual carriageway against the single carriageway section being improved.

26 TAG Unit A1.3, User and Provider Impacts, March 2017

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A limitation of this method is that it only considers current traffic flows and journey time reliability and not future year traffic flows and reliability, which could lead to an understatement of benefits attributable to the Scheme. However, it does at least quantify the benefits and is an advance on the qualitative reference to CRF (Congestion Reference Flow), or stress, contained in current guidance. It provides a conservative assessment for a single carriageway to dual carriageway scheme improvement that DfT has previously accepted. Benefits were calculated for a 60-year period and discounted to 2010 following TAG Unit 3.5.4. The present value of the reliability benefits for the Scheme over the 60-year appraisal period was calculated as £83.0 million (2010 prices discounted to 2010).

5.4 Comparison of costs and benefits (including alternative growth scenarios) Initial benefit to cost ratio (BCR) The initial (unadjusted) BCR is presented in Table 5-17. All costs and benefits are expressed in 2010 prices and are discounted to 2010. An appraisal period of 60 years was used, from 2025 to 2084.

Table 5-17: Economic Appraisal Summary – Initial BCR

2010 Prices discounted to 2010 Costs and Benefits (£000s)

Journey time savings 711,670

Vehicle operating costs -123,105

User Charges (Tolls) 0

Private Sector Revenue (Tolls) 0

Delays During Construction -34,740

Total Economic Efficiency 553,826 Benefits Benefits Monetised Noise Benefits 2,157

Monetised Air Quality Benefits -777

Carbon Benefits (Greenhouse Gas) -127,043

Accident Benefits 29,528

Indirect Tax Revenue 83,777

Present Value of Benefits (PVB) 541,468

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2010 Prices discounted to 2010 Costs and Benefits (£000s)

Construction Cost 435,603

Costs Operating and Maintenance 27,550

Present Value of Cost (PVC) 463,153

Net Present Net Present Value (NPV) 78,315 Value

Benefit Cost Benefit to Cost Ratio (BCR) 1.2 Ratio

Table 5-17 shows that the transport and economic efficiency benefits to road users amount to £553.8 million. Further benefits / disbenefits are then included as follows: a. Benefits through accident savings of £29.5 million b. Environmental benefits are assessed as: i. -£127.0 million from increased greenhouse gas emissions. ii. -£0.8 million from local air quality impacts. iii. £2.2 million from Noise impacts. c. Indirect tax revenue benefit of £83.8 million. The total Present Value of Benefits (PVB) amounts to £541.5 million. This compares to the Present Value Cost (PVC) of £463.2 million. The Net Present Value (NPV) of the Scheme is the difference between the Present Value of Benefits (PVB) and the Present Value of Cost (PVC). The NPV for the Scheme is calculated as £78.3M, which indicates a positive return on investment. The calculated initial Benefit to Cost Ratio (BCR) is 1.2. The summary of the main outcomes from TUBA for the Core Scenario are shown in Table 4-15 in the EAR, Appendix D to the ComMA, which also provides a breakdown by type of user. The full Analysis of Monetised Costs and Benefits (AMCB) table is presented in Appendix D of the EAR, Appendix D to the ComMA. An aggregated version is also given in Table 5-18.

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Table 5-18: Aggregated AMCB Table (£000s Discounted and Deflated to 2010)

Overall Impact Costs and Benefits

Present Value of Benefits (PVB):

Noise Benefits 2,157

Local Air Quality Benefits -777

Greenhouse Gases Benefits -127,043

Accident Benefits 29,528

TEE Benefits 553,826

Indirect Tax Revenues 83,777

Total PVB 541,468

Present Value of Costs (PVC):

Broad Transport Budget 463,153

Total PVC 463,153

Net Present Value (NPV) 78,317

INITIAL BENEFIT COST RATIO (BCR) 1.2

Adjusted Benefit to Cost Ratio (BCR) The adjusted BCR builds on the initial monetised costs and benefits. As noted in paragraphs 5.3.35 to 5.3.45 above, the overall appraisal of the Scheme included an assessment of wider economic impacts and an assessment of the benefits resulting from more reliable journeys. The adjusted BCR is derived from the initial BCR and includes the wider economic impacts and journey time reliability benefits. The adjusted BCR for the Scheme (1.9) is shown in Table 5-19.

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Table 5-19: Adjusted BCR (£000s Discounted and Deflated to 2010)

Adjusted BCR

Initial Present Value of Benefits PVB 541,468

Wider economic impacts 258,673

Journey Time Reliability 83,032

Adjusted Present Value of Benefits (PVB) 883,173

Present Value of Costs (PVC) 463,153

Adjusted Net Present Value (NPV) 420,020

Adjusted BCR 1.9

High and low growth BCR In accordance with TAG Unit M4, two sets of traffic forecasts and economic sensitivities have been prepared, to represent High and Low traffic growth scenarios. For the High growth scenario, a proportion of the Base Year demand is added to the demand from the Core scenario on a matrix cell by cell basis. For the Low growth scenario, the same proportion of demand is removed from the Core scenario. Planning assumptions for infrastructure schemes and developments remained unchanged. This high and low growth economic assessment was limited to TUBA and CoBALT and wider economic impacts. These have been included in Appendix E of the EAR, Appendix D to the ComMA; therefore, journey time reliability, environmental benefits and delays during construction were constant between the three growth scenarios. The variation in the benefits leading to the adjusted BCR between Core, High and Low growth scenarios is presented in Table 5-20 (full breakdown in Table 4- 22 of the EAR, Appendix D to the ComMA).

Table 5-20: Adjusted BCR by Growth Scenario

Scenario Costs and Benefits Low Growth Core High Growth

Adjusted Benefit to Cost Ratio (BCR) 1.8 1.9 2.2

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High carbon BCR A High Carbon Sensitivity analysis has also been undertaken in light of the consideration DfT are giving to future changes to the greenhouse gas assessments. The High Carbon Sensitivity test gave a net disbenefit for carbon emissions of -£196.4M, thereby reducing overall benefits by £69.4 million. As shown in Table 5-21, including this higher disbenefit in the Scheme economics reduces the adjusted BCR from 1.9 to 1.8 (full breakdown in Table 4-23 of the EAR, Appendix D to the ComMA).

Table 5-21: Carbon Cost Impacts on Core Growth Adjusted BCR

Scenario Costs and Benefits Core Growth Core Growth Central Carbon Cost High Carbon Cost

Adjusted Benefit to Cost Ratio 1.9 1.8 (BCR)

5.5 ComMA data requirements Table 5-22 summarises the relationship between the ComMA report and other ComMA Packages for information in Chapter 5, and identifies where further information can be found in relation to data used in the development of the transport models.

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Table 5-22: ComMA Data Requirements Summary – Chapter 5

ComMA Reference to ComMA Package Requirement

The Appendix D of the ComMA, Economic Appraisal Package: Economic Assessment Report, January 2021. Specifically: Economic Chapter 2 – Introduction to Economic Appraisal Appraisal Approach Chapter 3 – Scheme Costs Chapter 4 – Economic Assessment Method

The Appendix D of the ComMA, Economic Appraisal Package: Economic Assessment Report, January 2021. Specifically: Chapter 3 – Scheme Costs Economic Appraisal Chapter 4 – Economic Assessment Method Results Appendix A – Scheme Cost Estimate from HECSD Appendix C – Public Accounts (PA) Table Appendix D – Analysis of Monetised Costs and Benefits

The Appendix D of the ComMA, Economic Appraisal Package: Economic Assessment Report, January 2021. Specifically: Sensitivity Tests Chapter 4 – Economic Assessment: Core Scenario Appendix E – Low, Core and High Growth Scenarios

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6 Summary

6.1 The Scheme The purpose of the Scheme is to address the problems of congestion, poor journey time reliability and poor resilience against incidents between the Black Cat and Caxton Gibbet roundabouts. The Scheme seeks to address these problems through the construction of a new 10 mile dual 2-lane carriageway from west of the A421/A1 Black Cat roundabout through to east of the A428/A1198 Caxton Gibbet roundabout.

6.2 Model development The A428 Strategic Traffic Model, used to support the Development Consent Order (DCO) application, is a new traffic model developed from Highways England’s South East Regional Traffic Model (SERTM). The A428 Strategic Traffic Model was developed to expand on the area that the previous traffic model covered, which was used in earlier PCF Stages, and it utilised more recent and robust traffic demand data. The model network has three different areas: a. Area of Detailed Modelling (AoDM) where the detail of the highway network is greater. b. Between the AoDM and the ‘buffer’ network, where the detail of the network is sparser. c. Buffer network representing the SRN and other major local roads. The suite of models follows the principles set in the DfT’s Transport Analysis Guidance (TAG), comprising a trip-end model, a variable demand model (VDM) and a highway assignment model (HAM). The Base Year models were built to represent an average peak hour for the following weekday time periods: a. Morning (AM) peak: an average hour of 07:00 - 10:00. b. Interpeak (IP) peak: an average hour of 10:00 - 16:00. c. Evening (PM) peak: an average hour of 16:00 - 19:00. The model user classes are: a. Car Employer’s Business. b. Car Commuting and Education. c. Car Other Purposes. d. LGV. e. HGV (OGV1 and OGV2). The generalised costs for the model are based on TAG Databook May 2019 values.

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The development of trip matrices, model link flow and journey time validation meet the TAG criteria.

6.3 Forecasts of future flows An Uncertainty Log for both developments and network changes was developed for the Scheme. The forecast trip matrices were developed by considering the proposed land use developments, background car traffic growth using NTEM v7.2 and freight growth using RTF 2018. The growth in car trips from developments and background growth is constrained to trip ends derived from NTEM at district level. For each forecast year, the trip matrices were also adjusted to reflect changes to the forecast travel demand in response to changes to the cost of travel by use of a variable demand model. Three different growth scenarios, Core, Low and High growth were modelled for each forecast year. Table 6-1 presents the forecast growth in annual average daily traffic (AADT) along the Scheme sections in the without-Scheme scenario. The busiest section of road throughout the forecast period is the A1 north of Black Cat (Section B) which has a two-way flow of 60,900 vehicles in 2015 rising to 73,600 in 2051, an increase of just over 20%. The next busiest sections are the A421 West of Black Cat (Section A) with 47,800 vehicles in 2051 followed by the A428 East of Caxton Gibbet (Section G) with 44,900 vehicles in 2051. Higher flows on these sections would be expected as they are dual carriageway standard. The busiest section of the A428 where it is single carriageway standard is between Wyboston and Barford Road roundabouts (Section C) with a 2051 two- way volume of 36,700 vehicles.

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Table 6-1: AADT Vehicle Flows (Two-Way) – Without-Scheme

2051 2025 2040 Without Section Description 2015 Without- Without- - Scheme Scheme Scheme

A A421, West of Black Cat 36,200 42,400 46,600 47,800

B A1, North of Black Cat 60,900 69,700 73,600 74,300

A428, West of Barford C 29,100 34,600 36,300 36,700 Road

D A428, East of Barford Road 18,900 28,600 33,100 35,100

E A428, West of B1040 24,400 27,700 30,700 31,400

A428, West of Caxton F 25,300 28,700 31,400 32,200 Gibbet

A428, East of Caxton G 33,800 37,200 41,800 44,900 Gibbet

Table 6-2 provides comparisons of AADT flows in 2025, 2040 and 2051 along the Scheme sections between the Core and Low growth scenarios without the Scheme. This shows little difference indicating that the existing A428 single carriageway route between Black Cat and Caxton Gibbet is at capacity.

Table 6-2: AADT Vehicle Flows (Two-Way) – Without-Scheme – Core and Low Growth Scenarios

2025 Without Scheme 2040 Without Scheme 2051 Without Scheme Core Low Core Low Core Low Section Description % % % of A428 diff diff diff AADT AADT AADT AADT AADT AADT from from from Core Core Core

A421, West A 42,400 42,600 0% 46,600 46,700 0% 47,800 48,300 1% of Black Cat

A1, North of B 69,700 69,400 0% 73,600 73,800 0% 74,300 74,900 1% Black Cat

A428, West C of Barford 34,600 33,900 -2% 36,300 35,700 -2% 36,700 36,400 -1% Road

A428, East D of Barford 28,600 28,700 0% 33,100 33,400 1% 35,100 35,800 2% Road

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2025 Without Scheme 2040 Without Scheme 2051 Without Scheme Core Low Core Low Core Low Section Description % % % of A428 diff diff diff AADT AADT AADT AADT AADT AADT from from from Core Core Core

A428, West E 27,700 27,300 -1% 30,700 30,300 -1% 31,400 31,100 -1% of B1040

A428, West F of Caxton 28,700 28,400 -1% 31,400 31,100 -1% 32,200 32,000 -1% Gibbet

A428, East G of Caxton 37,200 35,800 -4% 41,800 40,500 -3% 44,900 43,900 -2% Gibbet

Table 6-3 presents the forecast growth in annual average daily traffic (AADT) along the Scheme section in the with-Scheme scenario for the Core growth. a. The greatest proportional changes are on the existing A428 between Cambridge Road junction and Caxton Gibbet, respectively Sections E and F. These sections have forecast reductions in traffic volumes of around 95%. b. There are more modest reductions in flows on the A428 west of Cambridge Road (Sections C and D), as these sections continue to be used by traffic accessing or egressing St Neots. However, the reductions are still substantial at around 30% and 40% of the Without-Scheme volumes respectively. c. There is a reduction on the A1 between Black Cat and Wyboston (Section B) in the 2025 Opening Year, however there is a small increase up to 4% in 2051. d. There are substantial increases in traffic flows beyond the western and eastern ends of the Scheme (Section A and G), from 38% in 2025 to around 70% in 2051. The much higher increases compared to 2025 are due to both increases in the background traffic in the corridor and traffic generated by the large scale of local developments in the corridor. They result in additional congestion in the corridor in the DM scenario. e. Along the new route (Section H and I), there is forecast to be some 32,000 vehicles daily two-way on the western section west of the Cambridge Road junction and 48,000 on the eastern section east of the same junction. The latter volume includes the substantial volume of traffic that joins or leaves the A428 using the east facing slip roads. The 2040 volumes are some 35-40% higher than those in 2025, and the volumes in 2051 are around 5,000 higher than those in 2040.

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Table 6-3: AADT Vehicle Flows (Two-Way) – With-Scheme

2025 2040 2051 With- Without Without Without- Diff With- Diff With- Diff Section Description Sche - - Scheme (%) Scheme (%) Scheme (%) me Scheme Scheme

A421, West 42,400 58,700 38% 46,600 78,100 68% 47,800 84,600 77% A of Black Cat

A1, North of B 69,700 62,300 -11% 73,600 74,000 1% 74,300 77,500 4% Black Cat

A428, West C of Barford 34,600 22,300 -36% 36,300 26,500 -27% 36,700 28,700 -22% Road

A428, East D of Barford 28,600 14,500 -49% 33,100 19,200 -42% 35,100 21,800 -38% Road

A428, West E 27,700 1,200 -96% 30,700 1,500 -95% 31,400 1,800 -94% of B1040

A428, West F of Caxton 28,700 1,900 -93% 31,400 1,900 -94% 32,200 2,000 -94% Gibbet

A428, East G of Caxton 37,200 51,200 38% 41,800 64,800 55% 44,900 72,000 60% Gibbet

New A428, Black Cat to H Cambridge - 31,900 - - 45,400 - - 50,500 - Road junction

New A428, Cambridge Road I - 48,000 - - 63,800 - - 69,400 - junction to Caxton Gibbet

Table 6-4 shows the comparison of journey time changes in 2040. With the Scheme in place, journey times along the A421/A428 between Renhold junction and Cambourne junction are forecast to reduce from around 30 minutes to around 16 minutes at peak time in the peak direction. As the Scheme results in additional traffic to the west and east, the time saving from the M1 J13 to the M11 J14 is marginally less at around 12 minutes at peak times. Along the A1, from Letchworth to A1 (M) / A1307 junction, travel time savings are between 1.5 and 3.5 minutes in the With-Scheme scenario compared to the Without-Scheme scenario in 2040.

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Table 6-4: Comparison of Journey Time Changes in 2040 (Longer Routes)

2040 Change Change Without- With- BY from from Time Scheme Scheme Route Description Direction Without- Without- Period Time Time No. Scheme Scheme (mm:ss) (mm:ss) (mm:ss) (%)

EB 29:48 15:34 -14:14 -48% AM WB 26:34 15:08 -11:26 -43% A421/A428 (Renhold EB 26:26 14:40 -11:46 -45% A428 junction to IP Cambourne WB 28:09 15:51 -12:18 -44% Junction) EB 26:17 14:30 -11:47 -45% PM WB 30:41 16:19 -14:23 -47%

EB 52:13 40:27 -11:46 -23% AM WB 50:05 40:38 -09:27 -19% A421/A428 EB 47:48 36:58 -10:50 -23% (M1 Junction 13 1 IP to M11 Junction WB 49:06 38:24 -10:42 -22% 14) EB 51:55 41:10 -10:45 -21% PM WB 52:04 40:00 -12:04 -23%

NB 40:20 38:54 -01:26 -4% AM SB 46:15 43:33 -02:41 -6%

A1 NB 38:40 38:02 -00:38 -2% 2 (Letchworth to IP A1307 junction) SB 38:58 35:26 -03:31 -9%

NB 45:09 43:31 -01:38 -4% PM SB 39:53 36:26 -03:27 -9%

EB 48:21 45:18 -03:03 -6% AM A603/B1042 WB 47:19 46:23 -00:55 -2% (Cardington 7 junction to M11 EB 43:47 42:22 -01:25 -3% Junction 14) IP WB 45:04 43:15 -01:49 -4%

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2040 Change Change Without- With- BY from from Time Scheme Scheme Route Description Direction Without- Without- Period Time Time No. Scheme Scheme (mm:ss) (mm:ss) (mm:ss) (%)

EB 45:00 44:41 -00:19 -1% PM WB 49:40 47:00 -02:40 -5%

NB 26:46 26:47 00:01 0% AM SB 34:38 33:51 -00:46 -2% A1198 NB 26:42 26:55 00:14 1% (Royston 8 IP A505/A1198 to SB 27:39 27:28 -00:12 -1% A14 J24) NB 29:17 29:55 00:38 2% PM SB 28:05 28:14 00:09 1%

6.4 Summary of economic appraisal The appraisal of the Scheme showed that it would result in lower and more reliable travel times on the A421 / A428 corridor, as well as a reduction in the number of accidents and casualties on the network. The appraisal of the Scheme and its impacts has also shown that it would produce benefits to the wider economy. Table 6-5 summarises the benefits and costs of the Scheme for the Core, Low and High growth scenarios.

Table 6-5: BCR and Adjusted BCR for Core, Low & High Growth Scenarios (£000s Discounted and Deflated to 2010)

Benefits and Costs Overall Impact Low Core High

Operating costs 27,550 27,550 27,550

Investment costs 435,603 435,603 435,603 PVC Total Present Value of Costs (PVC) 463,153 463,153 463,153

Noise Benefits 2,157 2,157 2,157

Local Air Quality Benefits -777 -777 -777 PVB Greenhouse Gases Benefits -127,043 -127,043 -127,043

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Benefits and Costs Overall Impact Low Core High

Accident Benefits 29,596 29,528 28,598

TEE Benefits, including construction, of 498,816 553,826 636,026 which:

(… Commuting user benefits) (…105,045 (…115,794) (…134,903)

(… Other user benefits) (…177,906 (…187,759) (…206,451)

(… Business user benefits) (…215,866 (…250,273) (…294,673)

Wider Public Finances, of which: -78,500 -83,777 -89,067

(…- (…Indirect Tax Revenues, Operation) (…-83,919) (…-89,209) 78,642)

(…Indirect Tax Revenues, Construction) (…142) (…142) (…142)

Total Present Value of Benefits (PVB) 481,249 541,468 628,029

Net present Value (NPV) 78,317

INITIAL BENEFIT COST RATIO (BCR) 1.2

Agglomeration 228,216 230,456 284,979

Wider Economic Impacts – Increased 22,817 26,257 30,697 Output

Wider Economic Impacts – Labour 2,126 1,960 2,580 Supply

Wider benefits Wider Journey Time Reliability Benefits 83,032 83,032 83,032

Adjusted Present Value of Benefits 817,439 883,173 1,029,317 (PVB)

Adjusted Net Present Value (NPV) 354,288 420,022 566,165

ADJUSTED BENEFIT COST RATIO (BCR) 1.8 1.9 2.2

Sources of costs Scheme construction costs were provided by Highways England’s Commercial Services Division (HECSD) in May 2019. The cost estimate was based on a Regional Delivery Partnership (RDP) procurement route, with an expected outturn cost of £812.5 million (2019 Quarter 1 price base), including Portfolio risk. Operating and Maintenance (O&M) costs of the Scheme were provided by HECSD in July 2020. The expenditure profile was based upon the O&M cost

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estimates prepared in 2019 Q1 prices and then inflated to outturn costs using Highways England’s projected construction related inflation. This gave a net outturn O&M cost of £380.5 million. The costs were then discounted to 2010 which gave a PVC of £463.2 million in 2010 market prices. This comprised construction-related investment costs of around £435.6 million and operating and maintenance costs of £27.6 million. Sources of benefits The purpose of the Scheme is to address the problems of congestion, poor journey time reliability and poor resilience against incidents between the Black Cat and Caxton Gibbet roundabouts. The key transport user benefits are derived from reductions to delays and improved travel times and journey time reliability along the corridor. Other transport user benefits (and disbenefits) arise due to changes in the number of accidents; vehicle operating costs and associated tax revenues; and changes in greenhouse gas emissions, traffic noise and air quality. These are smaller in magnitude than the travel time benefits (with the arguable exception of greenhouse gas emissions). The Scheme also has wider impacts on the economy, resulting in benefits due to increased agglomeration and business output. This is due to the reductions in travel times, realised once the Scheme is implemented, increasing accessibility to areas of employment.

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Table 6-6 presents a summary of the key monetised benefits of the Scheme.

Table 6-6: Key Monetised Benefits and Costs

Category Benefits and costs in (£000s)

Consumer - Commuting User Benefits

Travel Time 141,956

Vehicle Operating Costs -17,757

During Construction -8,405

NET CONSUMER - COMMUTING BENEFITS 115,794

Consumer - Other User Benefits

Travel Time 311,952

Vehicle Operating Costs -110,157

During Construction -14,036

NET CONSUMER - OTHER BENEFITS 187,759

Business

Travel Time 257,763

Vehicle Operating Costs 4,810

During Construction -12,300

NET BUSINESS IMPACT 250,273

Safety

Accidents 29,528

Environmental Impacts

Noise 2,157

Local Air Quality -777

Greenhouse Gases -127,043

Landscape

Wider Economic Impacts

Agglomeration 230,456

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Category Benefits and costs in (£000s)

Market Competition 26,257

Labour Supply 1,960

Dependent Development / moving jobs 0

Developer contributions

Developer contributions 0

Other Impacts

Indirect tax Revenues 83,777

[Other - please specify] No other impacts

Costs Central Government Funding

Cost to Broad Transport Budget 463,153

Benefits and costs in 2010 market prices, discounted to 2010. Rounded to nearest million. Key quantified benefits and disbenefits Table 6-7 presents the key quantified benefits and disbenefits of the Scheme. The contribution of the Scheme to various RIS 2 Key Performance Indicators (KPIs) can be found in the Client Scheme Requirements (CSR).

Table 6-7: Key Quantified Benefits and Disbenefits

Category Quantified Impacts Units

Journey times

Journey time savings

Safety

Accidents 600 (total number saved)

Fatalities 8 (total number saved)

Seriously injured 116 (total number saved)

Slightly injured 805 (total number saved)

Environmental Impacts

Number of Noise important areas - (number) affected

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Category Quantified Impacts Units

Bedford Town Centre AQMA, AQMA No. 4 Names of AQMAs Sandy, Brampton AQMA, (names)* Huntingdon AQMA and A14 Corridor AQMA.

Change in NOx emissions 62 (tonnes/year - in opening year)

Change in PM10 emissions Negligible (tonnes/year - in opening year)

Change in PM2.5 emissions 4 (tonnes/year - in opening year)

Change in greenhouse gas (CO₂) 3,313,000 emissions (tonnes - over 60y appraisal)

Customer Impact: Totals

Traffic delays due to Construction See below

Not assessed Traffic delays due to Maintenance quantitatively

Customer Impact: Per journey on A421/A1/A428; bidirectional, to nearest 10s

AM 01:30; IP 01:30; Traffic delays due to Construction (Phase (JT increase mm:ss by time 1) PM 01:40 period)

AM 05:30; IP 06:10; Traffic delays due to Construction (Phase (JT increase mm:ss by time 2) PM 05:40 period)

AM 05:40; IP 06:20; Traffic delays due to Construction (Phase (JT increase mm:ss by time 3) PM 05:10 period)

AM 05:40; IP 06:50; Traffic delays due to Construction (Phase (JT increase mm:ss by time 4) PM 05:30 period)

Not assessed Traffic delays due to Maintenance (Cars) quantitatively

Not assessed Traffic delays due to Maintenance (LGVs) quantitatively

Traffic delays due to Maintenance Not assessed (HGVs) quantitatively

*NB at all receptors considered within these AQMAs, changes are negligible or small.

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6.5 Consideration of results against scheme objectives Table 6-8 summarises the outcomes from the traffic and economics work which support the Scheme objectives:

Table 6-8: Summary of Objectives and Outcomes

Objective Outcome

One of the main objectives of the Scheme is to reduce journey times. With the Scheme in place, the traffic modelling work demonstrates that journey times are forecast to reduce by about 50% along the A421/A428 Renhold junction and Cambourne Connectivity: Cut congestion junction, from around 30 minutes to around 16 minutes at peak time and increase capacity and in the peak direction in 2040. As the Scheme results in additional journey time reliability between traffic to the west and east, the time saving from the M1 to the M11 Milton Keynes and Cambridge. is marginally less at around 12 minutes at peak times. There are also journey time savings along the A1 and on local routes, as shown in Table 4-7 and Table 4-8 in Chapter 4. Overall, this demonstrates that the Scheme meets the future needs of traffic for uncongested and reliable journeys.

• The number of observed accidents in along the A421 / A428 Safety: Improve safety at corridor is higher than would be expected, given the national junctions, side roads and accident rates for each year between 2011 and 2015 (apart from private accesses by reducing traffic flows on the existing 2015). CoBALT assessment (see A428. Improve safety on the Table 5-10) indicates that the total number of accidents saved by A1 by removing existing the Scheme is forecast to be 600 over the 60-year assessment substandard side road junctions and private accesses period; a clear positive impact. This saving consists of 8 fatal, 116 onto the carriageway. serious and 805 slight casualties (as each accident can have more than one casualty).

The wider impacts within the economy which have been estimated Economic growth: Enable demonstrate that the Scheme will have a positive impact on growth by improving agglomeration, output in imperfectly competitive markets, and connections between people labour supply – see Table 5-16 above. This positive impact is a and jobs and supporting new function of more efficient business operations (as a result of development projects. reduced journey times and improved reliability) and better access to labour.

Employing the Highways England biodiversity net gain calculation, Environmental a habitat-based metric, the Scheme achieves a net gain in improvements: Maintain biodiversity. In addition, enhancements will be achieved within the existing levels of biodiversity Scheme for certain habitats and species. and have a beneficial impact While air quality sees a small disbenefit as a result of the Scheme (- on air quality and noise levels £0.8m overall), in terms of noise, beneficial impacts are forecast for in the surrounding area. the three highest income groups, and neutral impacts for the two lowest income groups.

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7 Glossary

Abbreviation Phrase

AAD Average Absolute Difference

AADT Annual Average Daily Traffic

AAWT Annual Average Weekday Traffic

AMCB Analysis of Monetised Costs and Benefits

ANPR Automatic Number Plate Recognition

AoDM Area of Detailed Modelling

AST Appraisal Summary Table

ATC Automatic Traffic Count

AWT Average Weekday Traffic

BCR Benefit to Cost Ratio

BY Base Year

BYFM Base Year Freight Model

CAM Cambridgeshire Autonomous Metro

CIP Complex Infrastructure Project

CO2 Carbon Dioxide

COBA Cost Benefit Analysis

COBALT Cost and Benefit to Accidents – ‘Light Touch’

ComMA Combined Modelling and Appraisal

CSR Client Scheme Requirements

CSRM Cambridge Sub-Regional Model

DCO Development Consent Order

DF Design Freeze

DfT Department for Transport

DIA Distributional Impact Analysis

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Abbreviation Phrase Dynamic Integrated Assignment and DEmand DIADEM Modelling

DM Do Minimum

DMRB Design Manual for Roads and Bridges

DS Do Something

EAR Economic Assessment Report

EB Eastbound

ECML East Coast Main Line

EFT Emissions Factor Toolkit

ES Environmental Statement

EWR East West Rail

FY Forecast Year

GDP Gross Domestic Product

GPS Global Positioning Systems

HAM Highway Assignment Model

HECSD Highways England Commercial Services Division

HGV Heavy Goods Vehicle

IDC Intelligent Data Collection

ITN Integrated Transport Network

JT Journey Time

KPI Key performance Indicators

LGV Light Goods Vehicle

LMVR Local Model Validation Report

LPA Local Planning Authorities

LRoI Likely Region of Impact

LSOA Lower Layer Super Output Area

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Abbreviation Phrase MCLC Manual Classified Link Count

MCTC Manual Classified Turning Count

ME Matrix Estimation

MSOA Middle Layer Super Output Area

MyRIAD Motorway Reliability Incidents and Delays

NB Northbound

NO2 Nitrogen Dioxide

NOx Oxides of Nitrogen

NTEM National Trip End Model

NTM National Transport Model

NTS National Travel Survey

O&M Operation and Maintenance

OA Output Area

OAR Options Appraisal Report

OD Origin-Destination

OGV Other Goods Vehicles

OS Ordnance Survey

Ox-Cam Oxford to Cambridge

PA Public Accounts

PCF Project Control Framework

PCU Passenger Car Units

PIA Personal Injury Accidents

PM10 Particulate Matter 10

PM2.5 Particulate Matter 2.5

PPK Pence Per Kilometre

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Abbreviation Phrase PPM Pence Per Minute

PSV Public Service Vehicles

PVB Present Value Benefits

PVC Present Value of Costs

RAAD Relative Average Absolute Difference

RDP Regional Delivery Partnership

RIP Road Investment Programme

RIS Road Investment Strategy

RSI Roadside Interview

RTF Road Traffic Forecasts

RTM Regional Traffic Model

SB Southbound

SERTM South East Regional Traffic Model

SFC Speed Flow Curve

SGAR Stage Gate Assessment Review

SL Screenline

SMP Smart Motorway Projects

SOBC Strategic Outline Business Case

SRN Strategic Road Network

TA Transport Assessment

TAA Transport Assessment Annex

TAG Transport Analysis Guidance

TDCR Traffic Data Collection Report

TEE Transport Economic Efficiency

TEMPro Trip End Model Presentation Program

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Abbreviation Phrase TFR Traffic Forecasting Report

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TIS Traffic Information System

TLD Trip Length Distribution

TM Trafficmaster

TPG Transport Planning Group

TUBA Transport Users Benefit Appraisal

UL Uncertainty Log

VDM Variable Demand Model

VOC Vehicle Operating Cost

VoT Value of Time

WB Westbound

WITA Wider Impacts in Transport Appraisal

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Appendix A Transport Data Package: Traffic Data Collection Report (TDCR)

This appendix is presented in a separate document – Appendix A of the Combined Modelling and Appraisal (ComMA) Report.

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Appendix B Transport Model Package: Local Model Validation Report (LMVR)

This appendix is presented in a separate document – Appendix B of the Combined Modelling and Appraisal (ComMA) Report.

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Appendix C Transport Forecasting Package: Traffic Forecasting Report (TFR)

This appendix is presented in a separate document – Appendix C of the Combined Modelling and Appraisal (ComMA) Report.

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Appendix D Economic Appraisal Package: Economic Assessment Report (EAR)

This appendix is presented in a separate document – Appendix D of the Combined Modelling and Appraisal (ComMA) Report.

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Appendix E Economic Appraisal Package: Appraisal Summary Table (AST) and Supporting Worksheets Report

This appendix is presented in a separate document – Appendix E of the Combined Modelling and Appraisal (ComMA) Report.

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Appendix F Economic Appraisal Package: Distributional Impacts Report (DIR)

This appendix is presented in a separate document – Appendix F of the Combined Modelling and Appraisal (ComMA) Report.

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