HIGHWAY TRAFFIC ANALYSIS AND DESIGN Also by the late R.J. Salter Highway Design and Construction, second edition Traffic Ellgineering - Worked examples, second edition Other Macmillan titles of Interest to Civil Engineers Soil Mechanics - Principles and Practice G.E. Barnes Understanding Hydraulics Les Hamill Civil Engineering Materials, fifth edition edited by N. Jackson and R.K. Dhir Reinforced Concrete Design, fourth edition W.H. Mosley and J.H. Bungey Reinforced Concrete Desigll to EuroCode 2 W.H. Mosley, R. Hulse and J.H. Bungey Civil Ellgilleerillg Contract Administration alld COlltrol I.H. Seeley Civil Ellgineer;ng Qualltities, fifth edition I.H. Seeley Understanding Structures Derek Seward Surveying for Ellgineers, third edition J. Uren and W.F. Price HIGHWAY TRAFFIC ANALYSIS AND DESIGN R.J. Salter (deceased) Formerly Reader in Civil Engineering, University of Bradford Revised by N.B. Hounsell Ufliversity of Southampton THIRD EDITION palgrave * © R. J. Salter 1974, 1976, 1989 © Y. Salter and N. B. Hounsell 1996 All rights reserved. No reproduction, copy or transmission of this publication may be made without written permission. No paragraph of this publication may be reproduced, copied or transmitted save with written permission or in accordance with the proviSions of the Copyright, Designs and Patents Act 1988, or under the terms of any licence permitting limited copying issued by the Copyright licensing Agency, 90 Tottenham Court Road, london W1 P OlP. Any person who does any unauthorised act in relation to this publication may be liable to criminal prosecution and civil claims for damages. The authors have asserted their rights to be identified as the authors of this work in accordance with the Copyright, Designs and Patents Act 1988. First edition 1974 Revised edition 1976 Reprinted 1978,1980 (with amendments) First paperback edition (with further amendments) 1983 Reprinted 1985 Second editon 1989 Third edition 1996 Published by PAlGRAVE Houndmills, Basingstoke, Hampshire RG21 6XS and 175 Fifth Avenue, New York, N. Y. 10010 Companies and representatives throughout the world PAlGRAVE is the new global academic imprint of St. Martin's Press llC Scholarly and Reference Division and Palgrave Publishers ltd (formerly Macmillan Press ltd). ISBN 978-0-333-60903-3 ISBN 978-1-349-13423-6 (eBook) DOI 10.1007/978-1-349-13423-6 This book is printed on paper suitable for recycling and made from fully managed and sustained forest sources. A catalogue record for this book is available from the British library. 10 9 8 7 6 5 4 3 08 07 06 05 04 03 02 01 Typeset by TIP International, Sutton Surrey Contents Preface vii PART I TRAFFIC SURVEYS AND PREDICTION 1 1. Introduction to the transportation planning process 3 2. The transportation study area 8 3. The collection of existing travel data 12 4. The external cordon and screenline surveys 18 5. Other surveys 22 6. Trip generation 26 7. Trip distribution 38 8. Modal split 55 9. Traffic assignment 63 10. The evaluation of transportation proposals 71 PART II ANALYSIS AND DESIGN FOR HIGHWAY TRAFFIC 89 11. The capacity of highways between intersections 91 12. Headway distributions in highway traffic flow 101 13. The relationship between speed, flow and density of a highway traffic stream 119 14. Traffic speed distributions and estimation 131 15. Highway link design 146 16. Intersections with priority control 159 17. Driver reactions at priority intersections 166 18. Capacities and delays at priority intersections 173 19. A simulation approach to delays at priority intersections 182 20. Roundabout intersections 193 21. Grade-separated junctions and interchanges 202 22. Merging, diverging and weaving at grade-separated junctions and interchanges 215 23. Queueing processes in traffic flow 222 24. Geometric delay at non-signalised intersections 232 25. The environmental effects of highway traffic noise 236 26. The environmental effects of highway traffic pollution 253 27. Traffic congestion and restraint 259 PART III TRAFFIC SIGNAL CONTROL 271 28. Introduction to traffic signals 273 29. Warrants for the use of traffic signals 276 v vi CONTENTS 30. Staging and phasing 281 31. Signal aspects and the intergreen period 283 32. Signal control strategies 286 33. Geometric factors affecting the capacity of a traffic signal approach 292 34. The effect of traffic factors on the capacity of a traffic signal approach 296 35. Determination of the effective green time 301 36. Optimum cycle times for an intersection 304 37. The timing diagram 311 38. Early cut-off and late-start facilities 314 39. Opposed right-turning vehicles and gap acceptance 318 40. The ultimate capacity of the whole intersection 322 41. The optimisation of signal-approach dimensions 325 42. Optimum signal settings when saturation flow falls during the green period 330 43. Delay at signal-controlled intersections 335 44. Average queue lengths at the commencement of the green period 344 45. Programs for traffic signal design 350 46. The co-ordination of traffic signals 355 47 Time and distance diagrams for linked traffic signals 358 48. Platoon dispersion and the linking of traffic signals 363 49. The prediction of the dispersion of traffic platoons downstream of signals 367 50. The delay/offset relationship and the linking of signals 370 51. Urban traffic control systems 379 Appendix: Definitioll of symbols used ill Part III 388 Illdex 390 Preface More than three decades have passed since transportation and highway traffic engineering became recognised as an academic subject in the United Kingdom. During this period, significant advances have been made in traffic engineering theory and practice, against a background of ever increasing mobility and travel demand. Considerable interest has also developed in the economic, social and environmental costs of highways and other transport systems. Richard Salter's book on Highway Traffic Analysis and Design was first pub lished in 1974 and has proved an invaluable text-book for students specialising in Transportation Planning and Engineering in many Institutions of Higher Education in the United Kingdom as well as for many practitioners. The attraction of the book has been the concise and thorough way in which the many aspects of traffic analysis and design are presented, supported by numerous examples and 'question and answer' material. Sadly, Richard Salter died in 1992. For the book to reflect recent developments in the traffic engineering field, Nick Hounsell has now revised and updated rele vant sections of the book, while maintaining its qualities and basic structure. The book is presented in three parts. Part I covers traffic surveys and prediction. This provides an introduction to the transport planning process and descriptions of data collection methods and of the four-stage modelling process of trip generation, trip distribution, modal split and traffic assignment. Recent modelling software is also described. Part I concludes with a consideration of evaluation methods for transportation proposals. Part II of the book covers traffic analysis and design, starting with explanations of traffic flow theory and relationships between the main elements of speed, flow, density and capacity on highway links. A new chapter on geometric design of highway links is included. Part II then covers non-signalised junction design in detail, including priority junctions, roundabouts and grade-separated intersections. Computer-aided design techniques are included. Part II concludes with a consid eration of the environmental effects of traffic noise and pollution and the equally topical issue of traffic congestion and restraint. Part III of the book is devoted to traffic signal control. All issues of design and evaluation for isolated signals and urban traffic control systems are described in detail, including recent developments in computer programs for traffic signal design. Dr Salter was particularly grateful to the many colleagues and students who made valuable comments on the contents of the first and subsequently revised edi tions. This edition contains many of the suggestions they made. Dr Salter also expressed his appreciation to the following bodies for permission to reproduce their copyright material: Acer Consultants, Bedfordshire County Council, the vii viii PREFACE Building Research Station, the Department of the Environment, the Eno Foundation, the Greater London Council, the Institution of Civil Engineers, the Institution of Highway Engineers, National Research Council, Royal Borough of New Windsor, Traffic Engineering and Control, the Transport Research Laboratory and Wilbur Smith and Associates. Crown copyright is reproduced with the permission of the Controller of HMSO. Nick Hounsell would also like to express his thanks to the Depar~ment of Transport and the Transport Research Laboratory, again for permission to repro duce their copyright material. In addition, he would like to thank Professor Mike McDonald and Dr Mazen Hassounah of the University of Southampton for their contributions to this third edition. PART I TRAFFIC SURVEYS AND PREDICTION 1