Intersections Without Traffic Signals Ii

In March 1988, an international workshop on intersections without traffic signals was held at the Ruhr-University in Bochum, Germany. The proceedings of this workshop were published by Springer 1). The workshop was performed in a very harmonious atmosphere, which stimulated the experts from different countries to communicate and exchange their ideas and experiences. The presentations and the written contributions documented the present state of technical solutions for design and engineering of unsi gnalized intersections both regarding scientific research and practical applications. Moreover, numerous unsolved problems were identified. Thus, the 1988 workshop stimulated new developments in the field of unsignalized inter sections in several countries. In the meantime, these investigations have lead to a remarkable progress. For example in Germany a new guideline for unsignalized cross intersections and T-junctions has been finished and is going to be introduced in 1991. New results on roundabout capacity have been worked out as well. Many particularly important developments were made in foreign countries. Especially in the United States, an increasing interest in this subject can be observed. In the annual meetings of the TRB, this item received great attention. Many research institutes in North America have concentrated their activities on that point. A new TRB-circular concerning unsignalized intersections is going to be published. It will contain a new procedure for four-way-stop-control intersections, which seems to be a special feature of North American traffic engineering. However, new results from the US for two-way-stop control intersections are available as well.

In March 1988, an international workshop on intersections without traffic signals was held at the Ruhr-University in Bochum, Germany. The proceedings of this workshop were published by Springer 1). The workshop was performed in a very harmonious atmosphere, which stimulated the experts from different countries to communicate and exchange their ideas and experiences. The presentations and the written contributions documented the present state of technical solutions for design and engineering of unsi gnalized intersections both regarding scientific research and practical applications. Moreover, numerous unsolved problems were identified. Thus, the 1988 workshop stimulated new developments in the field of unsignalized inter sections in several countries. In the meantime, these investigations have lead to a remarkable progress. For example in Germany a new guideline for unsignalized cross intersections and T-junctions has been finished and is going to be introduced in 1991. New results on roundabout capacity have been worked out as well. Many particularly important developments were made in foreign countries. Especially in the United States, an increasing interest in this subject can be observed. In the annual meetings of the TRB, this item received great attention. Many research institutes in North America have concentrated their activities on that point. A new TRB-circular concerning unsignalized intersections is going to be published. It will contain a new procedure for four-way-stop-control intersections, which seems to be a special feature of North American traffic engineering. However, new results from the US for two-way-stop control intersections are available as well.

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.

This book deals with unsignalized intersections in road networks. It focuses both on mathematical procedures for calculating the capacity and the quality of traffic flow and on the conversion of the theories into practicable calculation methods. The state of the art and future developments from 8 countries (Australia, Czechoslovakia, F.R. of Germany, France, Poland, Sweden, U.K. and U.S.A.) are presented. Special emphasis is placed on methods of computer simulation. The reader will learn about the present state of international practice, about practical experience with approaches in different countries, and about the most recent scientific findings in the area of unsignalized intersections. Researchers will see here the trends of future research. Aspects of traffic safety are also dealt with. The traffic engineer primarily interested in applicable solutions is provided with practicable calculation methods, above all from the field of simulation techniques, and will be able to see which has the most promising future.

This book deals with unsignalized intersections in road networks. It focuses both on mathematical procedures for calculating the capacity and the quality of traffic flow and on the conversion of the theories into practicable calculation methods. The state of the art and future developments from 8 countries (Australia, Czechoslovakia, F.R. of Germany, France, Poland, Sweden, U.K. and U.S.A.) are presented. Special emphasis is placed on methods of computer simulation. The reader will learn about the present state of international practice, about practical experience with approaches in different countries, and about the most recent scientific findings in the area of unsignalized intersections. Researchers will see here the trends of future research. Aspects of traffic safety are also dealt with. The traffic engineer primarily interested in applicable solutions is provided with practicable calculation methods, above all from the field of simulation techniques, and will be able to see which has the most promising future.

Prediction of traffic (like weather forecast), its planning and control are counted among the great scientific and technological challenges. Similarly, flow of granular material like tablets or powders is of immense importance for industrial processing of solids. Both fields have intriguing conceptual analogies.From 9-11 October, 1995, the German Supercomputing Center HLRZ (Höchstleitungsrechenzentrum) at the research center Jülich (KFA) organized an international workshop 'Traffic and Granular Flow'. The purpose of this workshop was to promote the interaction between these two scientific fields, to which supercomputing is making essential contributions, and to stimulate the transfer between basic and applied research.

Before they begin their university studies, most students have experience with traffic signals, as drivers, pedestrians and bicycle riders. One of the tasks of the introductory course in transportation engineering is to portray the traffic signal control system in a way that connects with these experiences. The challenge is to reveal the system in a simple enough way to allow the student "in the door," but to include enough complexity so that this process of learning about signalized intersections is both challenging and rewarding. We have approached the process of developing this module with the following guidelines: * Focusing on the automobile user and pretimed signal operation allows the student to learn about fundamental principles of a signalized intersection, while laying the foundation for future courses that address other users (pedestrians, bicycle riders, public transit operators) and more advanced traffic control schemes such as actuated control, coordinated signal systems, and adaptive control. * Queuing models are presented as a way of learning about the fundamentals of traffic flow at a signalized intersection. A graphical approach is taken so that students can see how flow profile diagrams, cumulative vehicle diagrams, and queue accumulation polygons are powerful representations of the operation and performance of a signalized intersection. * Only those equations that students can apply with some degree of understanding are presented. For example, the uniform delay equation is developed and used as a means of representing intersection performance. However, the second and third terms of the Highway Capacity Manual delay equation are not included, as students will have no basis for understanding the foundation of these terms. * Learning objectives are clearly stated at the beginning of each section so that the student knows what is to come. At the end of each section, the learning objectives are reiterated along with a set of concepts that students should understand once they complete the work in the section. * Over 70 figures are included in the module. We believe that graphically illustrating basic concepts is an important way for students to learn, particularly for queuing model concepts and the development of the change and clearance timing intervals. * Over 50 computational problems and two field exercises are provided to give students the chance to test their understanding of the material. The sequence in which concepts are presented in this module, and the way in which more complex ideas build on the more fundamental ones, was based on our study of student learning in the introductory course. The development of each concept leads to an element in the culminating activity: the design and evaluation of a signal timing plan in section 9. For example, to complete step 1 of the design process, the student must learn about the sequencing and control of movements, presented in section 3 of this module. But to determine split times, step 6 of the design process, four concepts must be learned including flow (section 2), sequencing and control of movements (section 3), sufficiency of capacity (section 6), and cycle length and splits (section 8). Depending on the pace desired by the instructor, this material can be covered in 9 to 12 class periods.