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."

Anyone who reflects on the future of society cannot do so without at the same time thinking about the future of our transportation systems. The dilemma is obvious. On the one hand, mobility must be maintained as it is crucial to economic development and because people are eager for individual mobility. On the other hand, traffic imposes heavy burdens on people and on the environment, on cities and communities and on our national economies. Finding a solution to that dilemma seems to be difficult, in fact we have not even developed a rough idea of how it could look like. This is why the North Rhine-Westphalia Science and Research Ministry came up with the plan to work out a well-founded scientific basis on which to solve the problems inherent in our transport system. A research network has been established and sponsored with government funds for a period of three years with a view to realising that objective. The "Traffic Simulation and Environmental Impact" research network is composed of researchers who have an excellent reputation as North Rhine-Westphalia traffic experts. Cutting across various disciplines of knowledge, the network aims to integrate transportation and natural sciences, particularly physics and mathematics, in a move to profit by the synergy between technical know-how and innovative methodology. The present volume is intended as a progress report and a prologue to the forthcoming international colloquium which represents the highlight and at the same time the end of the three-year project funding period.