Werner Brilon (Editor) Intersections without Traffic Signals Proceedings of an International Workshop 16-18 March, 1988 in Bochum, West Germany With 88 Figures Springer-Verlag Berlin Heidelberg New York London Paris Tokyo Prof. Dr.-Ing. Werner Brilon Institut flir Verkehrswesen I Ruhr-Universitat Bochum UniversitatsstraBe 150 4630 Bochum This workshop was made possible by the generous support of the following organisations: Forschungsgesellschaft flir StraBen-und Verkehrswesen (German Road and Traffic Research Association) Deutsche Forschungsgesellschaft (German Council for Research) ISBN- 13: 978-3-642-83375-5 e-ISBN- 13: 978-3-642-83373-1 DOl: 10.1007/978-3-642-83373-1 This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, re-use of illustrations, recitation, broad casting, reproduction on microfilms or in other ways, and storage in data banks. Duplication of this publication or parts thereof is only permitted under the provisions of the German Copyright Law of September9, 1965,in its version ofJune 24, 1985,and a copyright fee must always be paid. Violationsfall under the prosecution act of the German Copyright Law. © Springer-Verlag Berlin Heidelberg 1988 Softcover reprint of the hardcover 1st edition 1988 The use ofr egistered names, trademarks, etc. in this publication does not imply, even in the absence ofa specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. 216113020 543210 Preface From March 16 - 18, 1988, an international workshop on inter sections without traffic signals will take place at the Ruhr University, Bochum. This book, which was compiled prior to the event, comprises the written versions of the contributions pre sented at the workshop. This preface is an attempt to give a short survey of the deve lopment of this particular field of traffic engineering. It has to be said in advance, however, that it is written from a point of view decisively influenced by the relevant German litera ture. Most of the intersections in our road networks are unsignaliz ed. At first glance, however, traffic engineers seem to be more interested in high-performance grade-separated or signalized intersections. But a closer study of the relevant literature does not confirm this apparent lack of importance. On the contrary: The subject of unsignalized intersections is still intensively dealt with at many research institutes. The German observer will notice the following fact while study ing the relevant sources: A remarkably high number of the au thors who have contributed to the investigation of unsignalized intersections in German-speaking countries have later become uni versi ty teachers. There is every reason to believe that traffic engineers primarily interested in theoretical problems have mainly been working in this field. The discussion of this subject up to the present can be subdi vided in several phases. However, the term "phase" is not meant in the sense of a strict temporal sequence; the phases are rather marked by factual aspects. In the first phase, the consideration of the capacity of inter sections began with merely deterministic modelling concepts, as VI it used to be common practice in traffic engineering. The works of Llibke ( 1931) or Bachmann ( 1943) may serve as examples of these concepts, however, this list is undoubtedly incomplete. These deterministic models were presumably influenced by the very low density of traffic at that time. In the USA, where high concentrations already occurred in the 1930s, the stochastic modelling concepts of traffic flow were founded with the work of Adams (1936). This idea was taken up in the German-speaking countries after 1950; the works of Grabe (1954), Leutzbach (1956), and Krell (1958) were of great importance. With regard to unsignalized intersections, the stochastic theory required findings about the so-called critical gap, la ter about move-up times as well, for the crossing of priority streams. This theory of critical gaps can be considered as the second phase in the investigation of unsignalized intersec tions. It is founded on the works of Greenshields (1947) and Raff (1950); in Germany, Retzko (1961) and Harders (1976) have contributed decisive results to it. The interest in critical gaps later decreased in the German-speaking countries, since Siegloch's research (1973) made a final clarification of the theoretical questions concerning this topic dispensible for practical purposes. In the English-speaking world, however, this topic is obviously still under discussion. There are numerous important contributions, e.g. by Ashworth (1970) and Hewitt (1985), to name only two. Contributions on the theory of critical gaps were also proposed for this workshop; due to the full agenda of the event, this topic unfortunately had to be omitted. The stochastic models of capacity and delay at unsignalized in tersections with stationary traffic conditions have to be re garded as the third phase of theories. These models are based on elements of the queueing theory almost without exception, although this was not explicitly made clear by the researchers dealing with it in the initial stage. In the German-speaking VII countries, the development lead from Grabe's approach (1954) and the contributions of Krell (1958), Dorfwirth (1961), and Worner (1963), to the work of Harders (1968), which was the ba sis of the practicable calculation method published by the Ger man Road and Traffic Research Association in 1972. This proce dure influenced the guidelines of several countries, the last one being the American Highway Capacity Manual of 1985. In Ger many, the theory was further developed by siegloch (1973), whose work still represents the latest findings of this third phase in the German-speaking countries. This development of the third phase also took place in the Eng lish-speaking world in a manifold way. From a German point of view, the results of Tanner (1962) and Buckley/Blunden (1963) are of particular importance. Of course there are numerous other contributions that cannot be mentioned here. In the Eng lish-speaking world, special emphasis was obviously put on the development of the theory. This development also lead to the derivation of very complex formulae for delay and congestion. In this respect, the works of Kremser (1962), Daganzo (1977), and Poeschl (1983) have to be mentioned. Even today, this development cannot be considered as being at an end. On the contrary, important contributions are published regularly, e.g. lately by Cowan (1987) and Golias (1986). The interested observer is struck by the extremely bad interna tional cooperation in this field in the course of the third phase. In Germany, for instance, there are publications from the end of the 1960s, which do not consider important basic formulae from English works. Partly, the same formulae were de rived by different authors obviously unaware of the other col league's research several years ago. On the other hand, the HCM adopted the German calculation method in 1985, when it had al ready become obsolete. This observation is one of the main rea sons for this workshop: By providing a forum for the discussion VII' of this particular field, the "time lag" in the exchange of results ought to be reduced. However, the development has meanwhile gone beyond the limita tions of the existing guidelines. This fourth phase is consti tuted by investigations of non-stationary traffic streams, i.e. of streams with volumes changing due to the time of day. This includes the investigation of temporary overload of the inter section, a problem overlapping with the analysis of non-poisson streams as well. Contributions dealing with this problem are also included in the program of the workshop. In Germany, substantial research with respect to these aspects was conducted by Professor Retzko in Darmstadt. The investiga tions of Stamm (1974), Tonke (1983), and BrUhl (1984) have to be mentioned. Another important contribution were the formulae derived by Jacobs (1979). In Great Britain, essential research was done by Kimber and Hollis (1979); unfortunately, their work has not found adequate attention in Germany up to now. This fourth phase of research is still continuing. The results are manifold and partly contradictory; even for a specialist it is no longer possible to have an overall view of this subject. One of the present tasks of academic teaching is undoubtedly to systematize the results of this field. However, the limitations of mathematical/analytical solutions for the problems of unsig nalized intersections become more and more apparent as well. Thus, the transition to the fifth phase - the simulation models - is fluid. At the moment, these approaches are of the greatest topicality, which is also indicated by the high number of con tributions on this subject submitted for the workshop. There fore, these works constitute a great part of this book. In the USA, early research on this subject is based on the work of Kell (1963). In the German-speaking countries, simulation models related to unsignalized intersections have a long tradi tion since the works of Steierwald (1961) and Bohm (1968). IX contrary to the earlier role of the simulation technique as an instrument of scientific research, today there is a trend to wards simulation as a practical tool for the daily work of the traffic engineer. Of course a final judgement of this concept cannot be given yet. The different simulation models will un doubtedly enter into a competition, maybe even across the na tional borders and language barriers. One aim of the workshop and of this book is to provide basic information about some of the "competitors". All previous remarks only referred to intersections which are not completely uncontrolled despite the absence of traffic sig nals: Priority has been assigned to some of the streams at the entry or intersection by traffic signs and traffic rules. Thus, two other kinds of junctions have not been treated so far: the intersection which is completely uncontrolled and the round about. In Central Europe, at uncontrolled intersections the traffic rule "priority to the right" is valid. About capacity estimation for this situation, only Vasarhelyi's work (1976) is known up to now. However, there is a considerable number of works published on roundabouts. Great Britain is undoubtedly the country in which roundabouts are most frequently built. From the vast number of published works only the important investigation of Kimber (1980) can be mentioned here. significant German research on this subject, e.g. by Lapierre (1959), was done decades ago. Roundabouts have obviously proven to be very efficient and safe in Great Britain. In recent years, this knowledge has gained acceptance in other countries as well, e.g. in Sweden, France, and - with a certain restraint - in the Federal Republic of Germany. Due to this development, a real renaissance of the roundabout can be expected for the future; and one working ses sion of the workshop is therefore devoted to this subject. Last but not least it has to be emphasized that the theory of the capacity of unsignalized intersections is not an end in itself in practical traffic engineering. The main aspect one x has to consider when deciding on the choice of traffic control devices at an intersection is traffic safety; in practice, ca paci ty is only of secondary importance. Therefore, the aspect of traffic safety at intersections has also been put on the agenda of the. workshop. Unfortunately, only one written version of the respective contributions was submitted on time before the printing of this book. with this international workshop, none of the topics mentioned before is considered as finished. On the contrary, the event mainly aims at providing an opportunity for learning and discussing the international state of the art in the field of unsignalized intersections. With the first eight contributions, this aspect of presenting both the calculation procedures cur rently employed and the most recent research projects takes up the greatest part of the workshop and of this book. All that remains is to hope that both the workshop and this vo lume improve the international cooperation in the field of un signalized intersections by providing comprehensive informa tion, and that both have a stimulating effect on the further development of this interesting and important aspect of traffic engineering. Bochum, January 1988 Prof. Dr.-lng. W. Brilon References Adams, W.F.: Road traffic considered as a random series. Jour nal of the Institution of Civil Engineers, 4, 1936, pp. 121- 130. Ashworth, R.: The Analysis and interpretation of gap acceptance data. Transportation Research, vol. 4, 1970. Bachmann, E.: Die Verkehrsleistung von Kreuzung und Kreisel: Landes-, Regional- und Ortsplanung. Beilage zu "Stra!3e uhd Verkehr", vol. 12, no. 1, Solothurn, Switzerland: 1943. Bohm, H.: Die Anwendung der Monte-Carlo-Methode in der Stra!3enverkehrstechnik, Teil I: Untersuchungen an ungesteuerten Knoten. Schriftenreihe "Stra!3enbau und Stra!3enverkehrstechnik", Heft 73, Bonn: 1968. BrUhl, F.: Spezielle Untersuchungen des Verkehrsablaufs auf zweispurigen Landstra!3en mit Hilfe der Simulation. Stra!3en- verkehrstechnik, Heft 4, 1984. Buckley, D.J., and Blunden, W.R.: Some delay-flow charac teristics for conflicting traffic streams. 2. Intern. Symposium on the Theory of Road Traffic Flow, London: 1963, p. 167. Cowan, R.: An extension of Tanner's results on uncontrolled in tersections. Queueing Systems, vol. 1, 1987, pp. 249-263. Daganzo, C. F.: Traffic delay at unsignalized intersections: Clarification of some issues. Transportation Science, vol. 11, no. 2, 1977. Dorfwirth, R.: Wartezei t und RUckstau von Kraftfahrzeugen an nicht signalgeregelten Verkehrsknoten. Forschungsarbeiten aus dem stra!3enwesen, Neue Folge, Heft 55, Kirschbaum Verlag, Bad Godesberg: 1961. Golias, J. C.: Towards a realistic analytical evaluation of minor-stream capacity at priority road junctions. Traffic Engineering and Control, Jan. 1986, pp. 2-5. Grabe, W.: Leistungsermittlung von nicht lichtsigna1gerege1ten Knotenpunkten des Stra!3enverkehrs. Forschungsarbei ten aus dem Stra!3enwesen, Neue Folge, Heft 11, Kirschbaum Verlag, Bielefeld (jetzt Bonn Bad Godesberg): 1954. Greenshields, B.D., Schapiro, D., Ericksen, E.L.: Traffic Performance at Urban Street Intersections. The Eno Foundation for Highway Traffic Control, Saugatuck, Conn.: 1947. Harders, J.: Die Leistungsfahigkeit nicht signalgeregelter stadtischer Verkehrsknoten. Schriftenreihe "Stra!3enbau und Stra!3enverkehrstechnik", Heft 76, Bonn: 1968.