Tfl Traffic Modelling Guidelines Version 3
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Traffic Modelling Guidelines TfL Traffic Manager and Network Performance Best Practice Version 3.0 MAYOR OF LONDON Edited by Dr James Smith & Robert Blewitt © Transport for London, September 2010 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 provided. Foreword 3 Foreword The capacity of London’s traffic network (both road and footway) is coming under increasing pressure and maintaining the smooth operation of this network is a challenging task. A primary goal of the TfL Traffic Manager is to deliver journey time reliability and it is essential that traffic schemes are developed to a high quality and their impacts on the network are well understood and mitigated with journey time reliability as the ultimate outcome. Traffic modelling plays an increasingly vital role in this objective and these guidelines provide invaluable support. They draw upon expertise from across the industry and form a comprehensive source of best practice. It is TfL’s remit to ensure that the effects of all planned interventions on the road network are thoroughly understood before they are implemented. These guidelines are fundamental in achieving this requirement. Alan Bristow TfL Streets Traffic Director Traffic Manager for TfL 4 Traffic Modelling Guidelines Acknowledgements The editors would like to thank the following individuals for their support during the creation of this document: John Green Operational Modelling, Traffic Directorate Kamran Hussain Operational Modelling, Traffic Directorate Ioannis Ioannidis Operational Modelling, Traffic Directorate Cyrus Kibuuka Operational Modelling, Traffic Directorate Vladimir Vorotović Operational Modelling, Traffic Directorate Glynn Barton Network Performance, Traffic Directorate Tony Earl Network Performance, Traffic Directorate Brett Little Network Performance, Traffic Directorate Jason Robinson Network Performance, Traffic Directorate Mangal Singh Network Performance, Traffic Directorate Ajay Tailor Network Performance, Traffic Directorate Neil Adams Traffic Infrastructure, Traffic Directorate Tim Piper Traffic Infrastructure, Traffic Directorate Nicola Cheetham Operations Directorate Steve Cotton Network Assurance Julie Dye Borough Projects and Programme Lorraine Johnson Roads Directorate John Lee Modal Policy Cycling Chris Lines Better Routes and Places Directorate Steve Miller Group Transport Planning and Policy Pam Turton Enforcement and Policing James Binning TRL Ltd David Carrignon Dessau Inc Nick Cottman Hyder Consulting Pty Ltd Samya Ghosh AECOM Ltd Matt Hall Atkins Global Ltd Derek Hooper MWH Australia Pty Ltd Dr Klaus Nökel PTV AG Contents 5 Contents Foreword 3 Acknowledgements 4 Introduction 12 PART A – MODELLING CONSIDERATIONS 15 1 Introduction 17 2 Background to Traffic Signal Scheme Modelling in London 19 2.1 Introduction 19 2.2 Legislative Responsibilities 20 2.2.1 Applying the NMD in TfL 20 2.2.2 Modelling Journey Time Reliability 21 2.3 Transport Modelling Hierarchy 22 2.3.1 Strategic 23 2.3.2 Cordon Area 23 2.3.3 Micro-simulation 23 2.3.4 Local Area 24 2.3.5 Operational 24 2.3.6 Model Integration 24 2.4 Modelling Standards 25 2.5 Fit for Purpose Modelling 25 2.6 Modelling Expertise 26 2.7 Site Visit and Data Collection 26 2.8 Assessing Future Scenarios 26 2.9 Modelling Boundary 27 2.10 Presentation of Modelling Results 27 2.11 Delivery of Traffic Modelling 28 3 Scheme Considerations 29 3.1 Introduction 29 3.2 Overarching Objectives 29 3.3 Interested Parties 29 3.4 Scheme Design 30 3.4.1 Junction Layout 30 3.4.2 Fixed Time and Adaptive Control 30 3.4.3 Traffic Signal Timing Plans 31 3.4.4 Contingency Signal Timings 31 3.4.5 24/7 Operation 31 3.4.6 Scheme Safety 32 4 General Traffic Considerations 33 4.1 Introduction 33 4.2 Route Choice for Local Modelling 33 6 Traffic Modelling Guidelines 4.3 When to move from Local Modelling to Strategic Modelling 34 5 Public Transport Considerations 35 5.1 Introduction 35 5.2 Assessment of Buses 35 5.3 Bus Stops 36 5.4 Bus Lanes & Pre-Signals 36 5.5 Bus Priority (BP) 37 6 Pedestrian Considerations 38 6.1 Introduction 38 6.2 Pedestrian Demand and Desire Lines 39 6.3 Isolated Pedestrian Crossings 39 6.4 Isolated Signalised Pedestrian Crossing Facilities 40 6.5 Pedestrian Facilities at Signalised Junctions 40 6.5.1 Full Pedestrian 41 6.5.2 Parallel Pedestrian 41 7 Cyclist Considerations 42 7.1 Introduction 42 7.2 Junction Design 42 7.3 Inclusion of Cyclists 43 8 Air Pollution Impacts 44 8.1 Introduction 44 8.2 TfL Objectives 45 9 Which Traffic Modelling Software? Why? 47 9.1 Introduction 47 9.2 Deterministic Models for Traffic Signal Control 48 9.2.1 Isolated Signalised Intersections 48 9.2.2 Isolated Non-Signalised Intersections 49 9.2.3 Networks 49 9.3 Micro-simulation Models 50 9.4 Assignment Models 51 PART B – MODELLING GUIDANCE 53 1 Introduction 55 2 Modelling Principles 57 2.1 Model Definitions 57 2.1.1 Model Scope 58 2.1.2 Base Model 58 2.1.3 Proposed Model 58 2.2 Model Auditing Process 59 2.2.1 Use of Approved TfL Models 60 2.3 Network Familiarisation 61 2.3.1 Model Boundary 61 2.3.2 Site Paperwork 62 2.3.3 Online Data Sources 62 2.4 Data Acquisition 63 Contents 7 2.4.1 Typical Traffic Conditions 63 2.4.2 Site Visits 64 2.4.3 Traffic Count Surveys 65 2.4.3.1 Passenger Car Unit 66 2.4.4 Private Transport Surveys 67 2.4.4.1 Cruise Times 67 2.4.4.2 Journey Times 68 2.4.4.3 Queue Lengths 69 2.4.5 Flared Approaches 69 2.4.6 Non-Green and Flashing Amber 69 2.4.7 Saturation Flow 70 2.4.7.1 Use of Calculation Formula RR67 71 2.4.8 Degree of Saturation 72 2.4.8.1 Underutilised Green Time 72 2.4.9 Signal Timings 75 2.4.9.1 UTC Junctions 75 2.4.9.2 Non-UTC Junctions 76 2.4.9.3 Demand-Dependent Stages 77 2.4.9.4 Pedestrian Facilities 77 2.4.10 Public Transport Surveys 78 2.4.10.1 Bus Route Frequencies 78 2.4.10.2 Bus Journey Times 78 2.4.10.3 Bus Stop Usage and Dwell Times 78 2.4.10.4 Bus Lane Usage 79 2.5 Model Development 79 2.5.1 Versions of Modelling Software 80 2.5.2 Base Model Calibration 81 2.5.3 Base Model Validation 81 2.5.4 Proposed Model Development 82 2.5.4.1 Changes to Junction Design 84 2.5.4.2 Changes to Traffic Flow 85 2.5.4.3 Demand Dependency Adjustments 85 2.6 Proposed Model Optimisation 86 2.6.1 Initial Optimisation 87 2.6.1.1 Underutilised Green Time (UGT) 87 2.6.1.2 Junction Storage Effects 89 2.6.1.3 Cycle Time Optimisation 89 2.6.1.4 Junction Performance 89 2.6.2 Optimisation Fine Tuning 90 2.6.2.1 Balancing the Network 90 2.6.2.2 Utilisation of Network Capacity 91 2.6.2.3 Protecting the Network 91 2.6.3 Proposal Evaluation & Impact Assessment 91 2.7 Model Reports 92 2.7.1 Calibration Report 92 2.7.2 Validation Report 93 8 Traffic Modelling Guidelines 2.7.3 Proposal Report 94 3 LinSig Modelling 95 3.1 Introduction 95 3.2 LinSig Version 3 96 3.3 Appropriate Use of LinSig 96 3.3.1 Skeleton Models 96 3.3.2 Isolated Junctions / Multiple Streams with Single Controller 97 3.3.3 Networks 97 3.3.4 Proposed Design Changes 97 3.4 LinSig Modelling Approach 97 3.5 Program Settings 98 3.5.1 Junction Details 98 3.5.2 Controller Details 98 3.6 Model Build 99 3.6.1 LinSig Model Structure 99 3.6.2 Traffic Flows 100 3.6.3 Routing / Lane Usage 100 3.6.4 Saturation Flows 101 3.6.5 Flare Usage 101 3.6.6 Priority Give-Way Parameters 102 3.6.7 Opposed Right-Turning Vehicles 102 3.6.8 Demand-Dependent Stages 102 3.6.9 Exit-blocking 103 3.7 LinSig Output 103 3.7.1 Link Results 103 3.7.2 Cyclic Flow Profile and Uniform Queue Graphs 103 3.7.3 Report Builder 104 3.8 LinSig Calibration Requirements 104 3.9 LinSig Validation Requirements 104 3.10 Developing Proposed Models 105 3.10.1 Cycle Time Optimisation 105 3.10.2 Signal Timing Optimisation 105 3.11 Additional LinSig Modelling Issues 105 3.11.1 Sliver Queues 105 4 TRANSYT Modelling 108 4.1 Introduction 108 4.1.1 TRANSYT 13 108 4.1.2 TranEd 109 4.1.3 Appropriate Use of TRANSYT 109 4.2 TRANSYT Modelling Approach 110 4.2.1 Program Settings 111 4.3 Model Build 112 4.3.1 TRANSYT Network Structure 112 4.3.2 TRANSYT Labelling Convention 114 4.3.2.1 Node Numbering 115 4.3.2.2 Traffic Link Numbering 115 Contents 9 4.3.2.3 Pedestrian Link Numbering 115 4.3.2.4 Exit Link Numbering 115 4.3.2.5 Priority Link Numbering 115 4.3.3 Node Input Data 116 4.3.3.1 Signalised Nodes 116 4.3.3.2 Non-Signalised Nodes 116 4.3.4 Link Input Data 116 4.3.4.1 Major Links 117 4.3.4.2 Minor Links 117 4.3.4.3 Signal-Controlled Links 118 4.3.4.4 Bottleneck Links 118 4.3.4.5 Give-Way Links 118 4.3.4.6 Flared Approaches 119 4.3.4.7 Pedestrian Links 119 4.3.4.8 Entry and Exit Links 120 4.4 Modelling Techniques 120 4.4.1 Flow Smoothing 120 4.4.2 Adjustment of Start and End Lags 121 4.4.3 Demand-Dependency 121 4.4.4 Exit-Blocking / Underutilised Green Time 122 4.4.5 Opposed Right-Turn Movements at Signals 122 4.4.5.1 Stop and Delay Weightings 123 4.4.5.2 Queue Limits 124 4.5 Public Transport 125 4.6 Calibrated TRANSYT Base Model 125 4.7 Validated TRANSYT Base Model 126 4.8 Developing Proposed Models 126 4.8.1 Modifying Network Structure 127 4.9 TRANSYT Network Optimisation 128 4.9.1 Cycle Time Optimisation 128 4.9.2 Signal Timing Optimisation 128 4.10 TRANSYT Output 129 4.10.1 .PRT File 129 4.10.2 Graphical Output 130 5 VISSIM Modelling 132 5.1 Introduction 132 5.1.1 Appropriate