Used to Evaluate U Nsignalized Intersections
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umber468 April 1997 · t.i\~~~ , AHVHBll OHYOB · _ ·· ~l· r----- ~! . ·~·, : 1661 tr I ~d\i H!>H'd3S3~ r~Olli! t! Od SNVH l Review of International Practices· Used To Evaluate U nsignalized Intersections TRANSPORTATION RESEARCH BOARD I NATIONAL RESEARCH COUNCIL TRANSPORTATION Number 468, April 1997 RESEARCH ISSN 0097-8515 CIRCULAR REVIEW OF INTERNATIONAL PRACTICES USED TO EVALUATE UNSIGNALIZED INTERSECTIONS COMMITTEE ON HIGHWAY CAPACITY AND QUALITY OF SERVICE Adolf May, Jr., Chairman Wayne K. Kittelson, Secretary Rahmi Akcelik Douglas W. Harwood Nagui M. Rouphail James A. Bonneson Michael Kyte Ronald C. Sonntag Werner Brilon Joel P. Leisch Alex Sorton Kenneth G. Courage Douglas S. McLeod Dennis W. Strong Rafael E. DeArazoza John Morrall Stan Teply Richard Dowling Barbara K. Ostrom Pierre-Yves Texier Daniel B. Fambro Ronald C. Pfefer Rod Troutbeck Ronald K. Giguere James L. Powell Thomas Urbanik II Fred L. Hall William R. Reilly John D. Zegeer Roger P. Roess Richard A. Cunard, TRB Staff Representative James P. Douglas, TRB Project Assistant Subscriber category Transportation Research Board IVA highway operations, capacity, National Research Council and traffic control 2101 Constitution Avenue, N.W. Washington, D.C. 20418 The Transportation Research Board is a unit of the National Research Council, which serves as an independent advisor to the federal government on .. scientific and technical questions of national importance. The Research Council, jointly administered by the National Academy of Sciences, the National .. Academy of Engineering, and the Institute of Medicine, brings the resources of the entire scientific and technical community to bear on national problems through its volunteer advisory committees. ACKNOWLEDGMENT This Circular was prepared by Dr. Werner Brilon (Ruhr University, Bochum, Germany), Dr. Rod Troutbeck (Queensland Universily of Technology, Brisbane, Australia), and Dr. Marion Tracz (Cracow Technical University, Cracow, Poland), internationally recognized experts in traffic flow theory at unsignalized intersections and members of the Unsignalized Intersection Subcommittee of the Committee on Highway Capacity and Quality of Service. In addition, members of the Unsignalized Intersection Subcommittee and of lhe Committee on Highway Capacity and Quality of Service provided review comments and suggestions related to all aspects of this document before its final approval and publication. - - TABLE OF CONTENTS BACKGROUND . 7 GAP ACCEPTANCE THEORY . 8 Usefulness of the Gaps . 8 Distribution of Gap Sizes in Priority Streams .............................................. 11 Hierarchy of Traffic Streams at a TWSC Intersection . ... .................................... 13 Capacity . 13 Quality of Traffic Operations/Queueing Theory ............................... .. ........... 15 M/G/1 System .............. ... .. .. ........................................... 16 M/G2/1 System ................................................... ............. 17 Queue Length ................................................................... 18 Time Dependent Solution ........... ........ .. ............... ... .............. ... 18 Conclusion to Queueing Theory ..................... ................................ 19 Stochastic Simulation ................................................................ 19 The Importance of Reserve Capacity . ... ..................... ............... .......... 20 Capacity for Streams of Rank 3 and Rank 4 ........ ......... .. ...... ... ..... ............ 20 Shared Lane Formula ............................................ .................. 22 Shared Lanes on the Minor Street ......................... .......................... 22 Shared Lanes on the Major Street .......................................... ...... ... 22 Conclusion to Gap Acceptance Theory ................ .................................. 23 EMPIRICAL REGRESSION THEORY ..................................................... 24 KYTE'S METHOD ........... .... .......................................... ... ........ 26 Evaluation of the Practices of Different Countries ........ ... ..... ............. ... ....... 26 AUSTRALIA ........................................................................ 27 AUSTROADS (1986) Technique .... .. ..... .......... .... .................. ...... 27 Bennett's Method ................ ........................................ ........ 28 THE FORMER CZECHOSLOVAKIA ........ .. ................................... .. ....... 28 GERMANY ........................................ .. ................. ............. 29 GREAT BRITAIN/UNITED KINGDOM ... ..... .... ........................................ 29 JAPAN ......................... ...................................... ........... 30 NETHERLANDS ................ ............. ... .. ... ... ........................... 31 NEW ZEALAND .............................................. ..... ....... .......... 31 Transit, New Zealand Method ............................... ......................... 31 Fisk Method ............................ ........................ ................ 31 POLAND .................................................................... ...... 32 SINGAPORE ........................................................................ 33 SWEDEN ............................. ..... ......................................... 33 UNITED STATES OF AMERICA ..................... .. .......... ... ................. 34 NOTATIONS • , . , . ... .... ... .. ..................................................... 35 REFERENCES ........... ...... ... ........... .. ................ .................... 36 - 7 BACKGROUND The design of unsignalized intersections has been given For capacity, the alternative rule ''Priority to the left11 different importance in different countries. In many would be more advantageous (Hondermarq, 1968). To countries, for instance in Australia and Germany, 4-leg some extent, the North American All-way-stop and T-iotersections are designed to meet safety controlled intersections (AWSC) operates quite similar. standards, not operational standards. Consequently A complete procedure of capacity calculation for this there is a requirement to ensure that adequate sight type has been given in TRB Circular No. 373 (TRB, distance is available. Under German conditions, mi:nor 1991) which is based on Kyte's research (Kyte, 1989). road approaches have been restricted to a one-lane An approximation of overall daily capacity of approach, to avoid mutual sight obstruction by cars. In intersections is as follows: these cases, it would not be expected that the capacity would be calculated when these unsignalized 1. uncontrolled 1000-1500 pcu/d intersections are constructed. However, with increasing (priority to the right) traffic volumes, the maximum capacity of these 2. yield or stop sign controlled 5000-12000 pcu/d intersections is becoming more and more important. 3. rotaries/roundabouts Therefore, particularly in a number of European single lane 20000-28000 pcu/d countries, a sophisticated series of procedures has been multilane 3500(}- ?1 pcu/d developed for the evaluation of capacity and traffic flow 4. signalized 200()(}-800002 pcu/d quality at unsignalized intersections. Previously, these 1 Varies from country to country procedures have mainly been used as a warrant for 2 installing a traffic signal at an intersection. More Depending on the no. of lanes for the different movements recently, these procedures are also being used in the network design process. When used in connection with This Circular concentrates on group 2, i.e. at-grade other traffic engineering capacity estimation procedures cross or T-intersections with one main street having (e.g. for signalized intersections), they serve to find stra priority over movements from the minor street. The tegies for traffic guidance in networks which help to subordination of the nonpriority streams is indicated by avoid the installation of traffic signals and reduce delays. a yield or stop sign, the American equivalent of which is Roundabouts, although unsignalized, should be 2-way-stop-controlled intersection (TWSC). considered differently from the cross- and T The Circular discusses the differences between the intersections. Some of the techniques used in the analysis techniques for TWSC intersections used in analysis of roundabouts can also be used in the appraisal different countries of the world. The practices are quite of signalized intersections (cf. Brilon, Stuwe, 1993; different and have different origins. Before discussing Troutbeck, 1993). the practices of individual countries, it is worthwhile to For uncontrolled intersections, we find the rule ''right discuss the desirable attributes of an analysis procedure. before left" or 1'right-of-way11 (when driving on the right Basically, we must distinguish between 2 different side of the street) in many countries (especially on the types of solutions for the analysis of TWSC traffic European continent, based on the early French highway operations: codes). A method of capacity estimation for this type of operation has been given by Vasarhely (1976). Several 1. Gap acceptance theory. authors have found that this basic rule of priority has 2. Empirical regression technique. neither a positive influence on safety nor on capacity. 8 GAP ACCEPTANCE THEORY Unsignalized intersections give no positive indication or USEFULNESS OF THE GAPS control to the driver. He/she is not told when he/she should enter the intersection. The driver alone must