Traffic Modelling Guidelines v4

1 5 TfL Traffic Modelling Guidelines Version 4 Traffic Modelling Guidelines Version Edited by Lucy Beeston, Robert Blewitt, Sally Bulmer and James Wilson Transport for London, September 2021 All rights reserved. Reproduction permitted for research, private study and internal circulation within an organisation. Extracts may be reproduced provided the source is acknowledged. Disclaimer This publication is intended to provide accurate information. However, TfL and the authors accept no liability or responsibility for any errors or omissions or for any damage or loss arising from use of the information Foreword Foreword London s roads have a vital role in realising the Mayor s vision for a fairer, greener, healthier and sustainable city.

2 The road network is changing to enable our customers, goods and services to move about the Capital more efficiently and safely especially for bus passengers, cyclists and pedestrians as part of the Mayor s vision. A primary goal of Transport for London s Traffic Manager is to maintain network availability to ensure reliable operations on the Transport for London Road Network (TLRN) and Strategic Road Network (SRN). It is essential that all schemes proposing changes to the way our roads operate are developed to a high quality, that the impacts on the wider network are well understood and mitigated, and the contribution to achieving Mayoral policy is considered. Operational Modelling plays a central role in all scheme development and design, both through the high-quality technical assessments which are important for developing scheme designs and supporting business decisions, but also in the Modelling information which stakeholders and customers have come to expect when they engage with scheme consultations.

3 These Guidelines provide valuable support to all transport professionals; they draw upon expertise from across the industry and form a comprehensive source of good practice. I hope you find them useful in your daily work and I welcome any feedback or ideas you have. This will ensure that together we can continuously improve the Guidelines for the benefit of everyone. Glynn Barton Director of Network Management Traffic Manager for TfL4 Traffic Modelling Guidelines Acknowledgements The editors would like to thank the following individuals for their significant contributions during the creation of this document: Helen Cansick Claire Kennedy Alexander Clewes Andrew Lovell Tony Dichev Abigail Moughal Vytas Dumbliauskas Paul Powell Mark Eady Birendra Shrestha John Green Pete Sykes Dan Hornshaw The editors would also like to thank.

4 Gareth Bek David Korzeniowski Ollie Benford Paul Moore Jim Binning Jonathan Morrow Mark Brackstone Carmen Muriana Cobo Claire Cheriyan John Nightingale Chris Davis Michael Oliver Andy Emmonds Georgia Perraki Alastair Evanson Charles Richardson Robin Forrest Simon Swanston Paul Harwood James Tate Tessa Hayman Sandra Weddell Lukas Kautzsch Domas Zemaitis Susanna Kerry Additionally, the editors acknowledge and appreciate all contributions from those not named who have participated in this and previous versions of the document. 5 Contents Contents Foreword 3 Acknowledgements 4 Contents 5 Introduction 26 Part A 27 Part B 27 Part C 27 About the Authors 27 PART A Modelling CONSIDERATIONS 28 1 Introduction to Part A 29 2 Background to Highway Scheme Modelling in London 31 Legislative Responsibilities 31 Scheme Definition 33 Applying the Network Management Duty in TfL 33 Traffic Signals 35 3 Modelling Overview 36 What is a Model?

5 36 Why Do Modelling ? 37 Basic Modelling Process 39 Replicating the Current Situation 39 Assessing Future Scenarios 39 Interpretation and Presentation of Modelling Results 40 Transport Modelling Hierarchy 41 Deterministic Modelling 41 Microsimulation Modelling 41 Tactical Modelling 43 Strategic Travel Demand Modelling 44 Model Integration 45 Three Stage Modelling 47 Modelling Standards 49 TfL Standards and Guidance 50 External Standards and Guidance 53 4 Stakeholder Engagement 54 Model Purpose 54 Key Stakeholders 55 Early Design Stages 55 Base Scoping Meeting 56 Modelling Scope 57 Site Visit and Data Collection 57 Modelling Expectations Document 58

6 Proposal Scoping Meeting 59 Strategy Considerations for Highway Scheme Development 59 Scheme Design 59 6 Traffic Modelling Guidelines Scheme Safety 60 Junction Layout 61 Network Operation 61 Design Refinement 62 Public Transport Considerations 62 Pedestrian Considerations 63 Cyclist Considerations 63 Emissions Considerations 65 Final Design Stages 68 Scheme Impact Report 68 Public Consultation 69 5 Which Traffic Modelling Software? Why? 70 Deterministic Models 74 Signalised Networks 75 LinSig 75 TRANSYT 77 Priority Junctions 78 Pedestrian Modelling 78 Microsimulation Models 80 Traffic 81 Aimsun Next 82 Vissim 82 Pedestrians 83 LEGION 84 Viswalk 84 Emissions 84 EnViVer 85 PHEM 85 Tactical Models 86 Aimsun Next 87 SATURN 87 Visum 87 6 Summary 89 PART B Modelling GUIDANCE 90 1 Introduction to Part B 91 2 Modelling Principles 93 Modelling Overview 94 Levels of Modelling 94 Deterministic Modelling 94 Microsimulation Modelling 95 Tactical Modelling 96 Pedestrian Modelling 96 Emissions Modelling 97 Common Model Simplifications 97 Early Design Stages 99

7 Three Stage Modelling Process 100 Stage 1: Base Model 101 7 Contents Stage 2: Future Base Model 101 Stage 3: Do Something 101 When to use the Three Stage Modelling Process 102 Scheme Assessments 102 Model Auditing Process 103 Scoping Meetings 105 Modelling Expectations Document 105 Planning a Modelling Project 107 Network Familiarisation 107 Modelling Purpose 107 Spatial Scope 108 Required Outputs 109 Modelling Software 109 Versions of Modelling Software 110 Planning Traffic Surveys and Data Collection 110 Data Collection 111 Existing Data Sources 111 Site Visits 113 Sample Size 115 Typical Traffic Conditions 116 Private Transport 116 Traffic Count Surveys 117 Passenger Car Unit 118 Cruise Times / Speeds 119 Journey Times 120 Queue

8 Lengths 121 Public Transport 122 Bus Journey Times 122 Bus Stop Usage and Dwell Times 123 Bus Lane Usage 123 Cyclists 124 Cyclist Counts 124 Cyclist Journey Times 124 Pedestrians 124 Signal Timings 125 Basic Principles 125 Types of Signal Control 128 UTC Junctions 129 Average SCOOT Timings 130 Non-UTC Junctions 131 Demand-Dependent Stages 132 Flared Approaches 133 Non-Green and Flashing Amber 133 Saturation Flow 134 Use of Calculation Formula RR67 136 Degree of Saturation 138 Underutilised Green Time 139 Measuring DoS 141 Base Model Development 145 8 Traffic Modelling Guidelines Base Model Calibration 146 Base Model Validation 147 Proposed Model Development 148 Future Base 151 The Scheme Proposal 151 Changes to Junction Design 152 Changes to Traffic Flow 153 Demand Dependency Adjustments 154 Public Transport Adjustments 155 Sensitivity Testing 155 Construction Phases 156 Interaction Between Modelling Levels 157 Model optimisation 158 Initial optimisation 160 Underutilised Green Time 162 Junction Storage Effects 162 Cycle Time optimisation 163 Junction Performance 164 Iteration with Tactical Models 165 optimisation Fine Tuning and Impact Assessment 165 Balancing the Network 165 Utilisation of Network Capacity 167 Protecting the Network 167

9 Interaction with Microsimulation Modelling 168 Improving the Design 168 On-Street Implementation 168 Model Assessment 170 Model Reporting 171 Calibration Report 171 Validation Report 172 Future Base Report 173 Proposed Model Report 174 Scheme Impact Report 175 Public Consultation 176 Presentation of Modelling Outputs 176 3D Modelling 177 3 Aimsun Next Modelling 180 Introduction 180 Introduction to Aimsun Next 180 Software Versions 181 Appropriate Use of Aimsun Next 181 Preparation 183 Model Boundary 183 Data Collection 184 Site Observation 184 Signal Timings 185 Saturation Flows 186 Journey Times 186 Public Transport 187 9 Contents Model Time Periods 187 Network Layout 188 Network Import 188 Transport Model Import 189 Background Import 190 Graphical User Interface 191 Base Model Calibration 193 Model Parameters 193 Simulation Step 193 Units 193 Rule of the Road 194 Network 194 Sections 194 Nodes and Turns 196 Junction Geometry 199 Side Lanes 200 Roundabout Geometry 202 Driving Behaviour 203 Traffic Data 205 Vehicle Types and Classes 205 Vehicle Network Entry 206 Warm-Up Demand 207 Public Transport 207 Pedal Cycles and Motorcycles 208 Pedestrians 209 Routing 209 OD Matrices 209 Traffic States 210 Route Choice Method 210 Signal

10 Control 214 Controller Logic 214 Demand-Dependent Stages 215 Pedestrian Phases 216 Give-Ways and Stoplines 217 Base Model Validation 218 Randomness 218 Validated Model Requirements 218 Traffic Flows 219 Saturation Flows 219 Demand Dependency 220 Journey Times 220 Queue Data 221 Public Transport 221 Check and Fix 221 Proposed Model Development 223 Future Base 223 Scenario-Based Workflow 223 Model Outputs 226 Methods 226 10 Traffic Modelling Guidelines Table View 227 Time Series 227 Validation 228 Database 229 Scripting 229 Data 229 Traffic Flows 230 Saturation Flows 231 Journey Times 231 Queue Data 232 Signal Timings 232 Vehicle Trajectory Files 232 4 LinSig Modelling 234 Introduction 234 Introduction to LinSig 234 Software Versions 235 Appropriate Use of LinSig 235 Junctions and Networks 235 Skeleton Models 236 Pedestrians 237 Proposed Design Changes 237 Preparation 238 Model Boundary 238 Data Collection 239 Model Time Periods 239 Graphical User Interface 240 Network Layout View 240 Error View 241 Scenarios 242 Controller Selection 242 Base Model Calibration 244 Calibrated Model 244 Network Settings 244 Network Structure 245 Junctions 245 Arms and Lanes 246 Connect