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.

3 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. 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.

4 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.

5 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.

6 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? 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

7 Key Stakeholders 55 Early Design Stages 55 Base Scoping Meeting 56 Modelling Scope 57 Site Visit and Data Collection 57 Modelling Expectations Document 58 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?

8 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

9 94 Microsimulation Modelling 95 Tactical Modelling 96 Pedestrian Modelling 96 Emissions Modelling 97 Common Model Simplifications 97 Early Design Stages 99 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

10 115 Typical Traffic Conditions 116 Private Transport 116 Traffic Count Surveys 117 Passenger Car Unit 118 Cruise Times / Speeds 119 Journey Times 120 Queue 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