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Über dieses Buch

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.

Inhaltsverzeichnis

Frontmatter

Current and Future Australian Practices for the Design of Unsignalized Intersections

Summary
The Australian State Road Authorities use two intersection design guides for the design of unsignalised intersections. This paper describes the gap acceptance methods of evaluating capacity described in these guides and compares them with the 1985 Highway Capacity Manual. There has been a number of recent Australian research papers on traffic flow theory based on the use of a dichotomised headway distribution. This research is also described here.
R. J. Troutbeck

The Design of Unsignalized Intersections in the UK

Abstract
The cost of traffic delays and accidents at road junctions in the UK is estimated at some £6,000M or so per year, and more than 50% of it comes from unsignalised junctions. Design practices, which bear directly upon the efficiency, and therefore the user cost, of junctions have been subject to much scrutiny over the past decade, and the methods now used incorporate the results of a programme of major research studies.
R. M. Kimber

Status of Unsignalized Intersection Capacity Research in the United States

Abstract
The most recent edition of the Highway Capacity Manual (HCM), was published in the United States in the fall of 1985. This publication (Special Report 209; Transportation Research Board; National Research Council) included a new technique for analyzing the capacity and level of service at unsignalized intersections.
John D. Zegeer

Safety and Design of Unsignalized Intersections in France

Summary
Extensive studies and experiments were recently undertaken in France with the aim of developing new concepts and criteria for junction design, especially regarding safety conditions.
The author presents the main results of these studies, as well as a general survey of French guidelines at their actual state of development for at-grade intersections and roundabouts.
J. M. Gambard

Research on Traffic Performance of Major/Minor Priority Intersections

Summary
The paper describes the state of polish experiences and guidelines as well as current research activities on traffic performance of major/minor priority intersections. In the first part, the background of the existing method and its structure is described. Attention is then focused on research activities leading to an improvement of the existing method for capacity analysis. The paper also presents some results of a comparison of the two techniques of capacity modelling. The basic ideas of the new method are then briefly described.
M. Tracz

Swedish Research on Unsignalized Intersections

Summary
The methods used by the Swedish National Road Administration to calculate capacity, delay, queue length etc in unsignalized intersections are based on a queuing theory model and on earlу german methods. These methods are used in the CAPCAL computer program, which was completed in 1977. However, the methods are now old and partially out of date since recent research and development have produced new and better empirical results, better theories, new calculation methods etc.
Hence, the Swedish National Road Administration is now revising the CAPCAL program in order tо update the present methods and also to introduce calculations of some new performance measures. The development of the methods was preceded by a literature survey and the following presents the proposed calculation procedures intended to replace the existing CAPCAL program for the evaluation of different performance measures at intersections without signals (but not roundabouts).
J. Anveden

Research on Unsignalized Intersections with Impact on the Czechoslovak Design Standard

Abstract
In the 1970s research into the capacity of the uncontrolled junction was carried out with the aim to find out a suitable method of capacity calculation applicable to the Czechoslovak standard ON 73 6102. Theoretically, the applied method was based on Harder’s principles and our knowledge gained from the investigation of critical gaps.
P. Jirava, P. Karlický

Recent Developments in Calculation Methods for Unsignalized Intersections in West Germany

Abstract
This paper gives a survey of the development of calculation methods for unsignalized intersections in Germany. First of all, some comments and critical notes on the German guideline published in 1972 and the procedures adopted in the HCM 1985 are given. Moreover, the present state of the art, which comprises the calculation of capacities and queues with stationary and partially non-stationary traffic streams by merely mathematical methods and by simulation models, is described. For future practical application in Germany, both a simple calculation method and a practicable simulation model are planned. However, with respect to the correct consideration of impedance effects of traffic streams at intersections, some theoretical questions still have to be discussed up till the introduction of a new guideline.
Werner Brilon

Some Factors Effecting Left-turn Capacity and Delay at Unsignalized Intersections

Summary
The theoretical models of traffic flow, e.g. the time gap acceptance model, are too much simplified in many aspects. In this paper, the gap acceptance model is analysed as a stochastic process. As a result of mathematical analysis, an expression of the cumulative probability of accepting time gaps has been calculated. Furthermore, the effect of pedestrians on left-turn capacity is discussed.
L. M. Hoppe, T. Krystek

A Model of Unsignalized Intersection Capacity Based on Erlang-3 Gap Distribution

Summary
A methodology is developed for the analysis of traffic flow at unsignalized intersections. Formulas for the estimation of the capacity of the minor street are derived analytically. The procedure can be applied to “T” intersections, as well as to four leg intersections with two lane major and /or two lane minor street, or minor street with a right turn bay.
The analysis incorporates three important features. The first is the modeling of the distribution of gaps formed on the major street by an Erlang- 3 distribution. Erlang-3 offers a more realistic fit to field conditions although it makes confutations cumbersome. The second feature is modeling accounting for the multiple utilization of gaps, while the third feature is the explicit recognition of the effects of vehicles sharing a common lane on the minor street.
Pano D. Prevedouros

The Influence of Partial Constraint on Delay at Priority Junctions

Abstract
In order to evaluate the level of service at priority junctions, delays are considered an important criterion in addition to capacity. In the following paper a simulation model is presented, in which delays under conditions of partially constrained, non-stationary traffic can be determined. Within this context, any possible traffic streams at intersections of two two-lane roads can be considered. With the simulation results the influence of partial constraint on delay has been evaluated.
Xiwen Zhang

Simulation Studies of the Effects of Some Geometrical and Traffic Factors on the Capacity of Priority Intersections

Abstract
In this paper, a simulation model of traffic at major/minor priority junctions is described. It has been used as a basic tool for the development of a practical method of capacity calculation. Some results of traffic performance studies at major/minor priority intersections conducted with the use of the described model are presented in the paper. The objective of the studies was the assessment of the effects of traffic restraints and platooning and its non-stationarity on capacity and traffic performance measures. The results of studies of the impedance effects are also presented in the paper.
Stanislaw Gaca, Janusz Chodur

INSECT - The Calibration and Validation of an Intersection Simulation Model

Abstract
This paper presents the calibration and validation of the INSECT model. INSECT is a vehicle by vehicle intersection simulation model for dealing with sign controlled intersections, roundabouts and more recently traffic signals. This paper covers the validation of non-signalised intersections. The calibration and validation indicated that the model gave good results across the whole range of intersections tested. The work has indicated that fixed gap times are not applicable either to individual intersection types or within intersection types. This is mainly due to the fact that there are different gap acceptance characteristics between sign controlled intersections and roundabouts. Also, that the gap accepted by the motorist is related to the time that they have waited. It is believed that INSECT is a useful tool for the evaluation of all types of intersections and it has recently been extended to cover traffic signals which will be the subject of a future paper. In addition, it is intended to extend the INSECT model to the accident prediction area where the number of conflicts can be determined automatically and the model used as a surrogate survey tool.
R. T. Tudge

Conflicts and Delay Studies at Unsignalized Intersections

Abstract
This paper describes simulation models for unsignalized intersections and signalized intersections. The number of conflicts and vehicle delays have been used to evaluate the level of service of unsignalized intersections, where the number of conflicts is used to evaluate the safety effects and delay is used in cost benefit analysis. A formula for calculating the number of conflicts at unsignalized intersections has been derived and is compared with the simulation results. It is concluded that the formula could be used for unsignalized intersections. At the end of this paper, several conclusions are drawn and suggestions are made for establishing signal control at unsignalized intersections.
Xiao Yan Zhang, Shu Sheng Zhang

Recent French Studies on Capacity and Waiting Times at Rural Unsignalized Intersections

Summary
Several studies have been undertaken in France during these last years in the field of capacity and delays at unsignalized intersections, in order to provide the engineer with some aids to design. This research, starting from an extensive comparison of the possible approaches, has led to the development of a microscopic simulation program (OCTAVE). Besides, a capacity formula for rural roundabout entries has been derived from measurements. This paper summarizes the main results of these studies.
Gérard Louah

KNOSIMO - A Practicable Simulation Model for Unsignalized Intersections

Abstract
The Simulation model KNOSIMO, which makes it possible to model the traffic flow at unsignalized intersections on a personal computer, was developed on behalf of the Federal Minister of Transport. KNOSIMO facilitates the reproduction of sequences of traffic volumes in all traffic streams for the whole day. The accuracy of the model’s results was proven by measurements. With the help of the simulation technique the program overcomes the theoretical problems of the traditional calculation methods. It is suited for immediate practical application, e.g. for answering the question whether traffic signals are necessary or not.
Michael Grossmann

UK Techniques for the Prediction of Capacities, Queues, and Delays at Intersections Without Traffic Signals

Abstract
The UK Transport and Road Research Laboratory (TRRL) has been concerned for many years now with techniques for predicting capacities, queues and delays at non-signalised road junctions. A separate paper [1] has outlined the background to the development of current practices; the aim of the present paper is to amplify the results and to describe how the techniques have been drawn together in two computer programs ARCADY2 and PICADY2. The programs calculate capacities, queues and delays at roundabouts and major/minor junctions respectively. They use information about arriving (demand) flows and junction geometry, and provide traffic engineers with essential aids in the design of non-signalised junctions. They have been in widespread use by local authorities and engineering consultants in the UK for a number of years and are used to an increasing extent in other countries.
Marie C. Taylor

Computer Assisted Optimisation of Roundabout Design

Summary
The development of low cost/high performance computers provides an excellent opportunity to develop better techniques for junction design. The Transport and Road Research Laboratory has developed ARCADY, a program to estimate the performance of a particular roundabout layout. In order to use ARCADY the traffic engineer has either to produce a preliminary layout drawing and extract the required geometric input to the program or make an educated guess at suitable parameters and if satisfactory, attempt to fit a layout to them. In either case a considerable amount of trial and error is likely to be involved.
This paper describes in some detail research undertaken at University College London to perform the task above wholly in the computer and with a minimum of user intervention. The paper describes the background to this research project, outlines current manual techniques for roundabout design and gives an overview of the methods and software developed. Two modes of operation are available: automatic design and user intervention; under the first one the software designs the smallest roundabout capable of coping well with traffic demand. The user intervention mode allows the engineer to override the automatic design features and use the package as an (intelligent) electronic drawing board coupled with a roundabout performance calculator. Later sections provide details of the optimisation procedures developed and describe our program for further research in this area.
L. G. Willumsen, W. Kay

Traffic Safety at Roundabouts

Summary
In general, the experience of roundabouts in Sweden is positive (these currently number about 150). In terms of totals, roundabouts give rise to approximately the same number of accidents in relation to the traffic volume as other types of junctions. However, the injury consequences are much lower in roundabouts. This is explained by the fact that the types of accidents with the highest injury consequences in normal junctions are replaced by a cor responding number of accidents with low injury consequences in roundabouts.
H. Å. Cedersund

Intersection Lay-out, Priority Rules and Traffic Safety

Summary
This paper reports on the accident-research carried out as part of a large project on priority-rules at intersection, started in 1983. For this accident-research an inventory was made of a large number of intersections. Recorded were lay-out features, accident data and traffic volumes. On a subset of these intersections detailed traffic counts were made. This paper deals with the preparations for this activity, the analysis and the results. The initial conclusions will be presented.
Frank Poppe

Backmatter

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