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Regelung in Verkehrssystemen
Abstract
Control in traffic systems: who doesn't think now of traffic lights and junctions? – Should it not be possible to control the traffic flow through a city in an optimal way? – It is possible, under one basic condition: one has to be able to measure the traffic flow and to use the data as input of the controller. The controller must have on-line access to the traffic data, and the decisions of the controller must be transmitted to the junction without time delays. The book presents an approach for developing a new, fully dynamic controller and shows also, with an example, how such a controller has to be implemented.
Vehicle detectors are measuring the traffic through data by each car or tram. The signals must be pre-processed in an observer and can then be used for determining the best sequence of phases for the near future. Vehicles, still being far away from the junction, have only little influence on these decisions. As soon as the input data has changed significantly, the phase sequence has to be re-calculated which makes the algorithm to be a repetitive optimization over a finite time horizon. The optimization itself is a multistage decision process and can be done therefore using Dynamic Programming; for shorter calculating time it is superposed by Branch and Bound.
The algorithm breaks with the very frequently used cyclic junction control and enables a fast reaction time on changing traffic situations. For the algorithm optimality criteria and objective functions can be formulated. Furthermore it is possible to give an absolute priority to the public transportation in form of trams or buses.
After an introduction, the second chapter shows the modelling and the mathematical description, as well as the structure and the details of the control algorithm. The implementation of the controller for a junction in Zurich is shown in the third chapter, and some results are given. Special attention is paid to the handling of erroneous or unreliable detector signals. An observer, using data filtering and synchronized simulation feeds the controller with reliable input data.
There are not only junctions with traffic lights in a city, and therefore the fourth chapter shows how to control streets with synchronized lights ("Green Waves"), and highway control for avoiding traffic congestion. Also the limitations of the algorithm are reached by applying it to more general problems in Queuing Theory.
Finally the fifth chapter describes the software developed and needed for designing a dynamic control for a traffic junction. These are a simulator, an observer, and the controller.
This doctoral thesis is only available in German.
Supplementary resource (1)
Es wird ein Algorithmus entworfen, der laufend verkehrsabhängige Daten einer Kreuzung und strategische Vorgaben des Verkehrsrechners verarbeitet, urn den jeweils nächsten Umlauf einer Ampelanlage zu planen.
In this paper the design of a controller crossing is presented by means of an example. The controller to be developed has to minimise the waiting time of the public transportation while maintaining the individual traffic flowing as well as possible. First, the model of the chosen traffic crossing is derived. Then, using a combination of ‘Dynamic Programming’ and ‘Branch and Bound’ the control algorithm is presented. A visualization of the algorithm is given by means of graphs, complexity issues are investigated, and computational refinements proposed. Simulation results are shown at the end. The actual implementation of the control algorithm for the example shown is under way and carried out in co-operation with the Transportation Authority of the city of Zurich. The work presented here is part of a bigger project. The overall goal is to provide the traffic engineer with a tool for designing ‘intelligent’ controllers for traffic lights.
This paper describes a new computer method, mixed-integer traffic optimization, designed to optimize simultaneously all the traffic control variables of the network. The method has been programmed in conjunction with the mixed-integer routine of IBM's MPSX optimization system and thus provides a globally optimal procedure. It was applied to several traffic signal networks and is shown to offer certain advantages over existing methods. An example is presented to illustrate the input requirements, output format, and application of the program.
The design of a controller for a traffic crossing is presented by means of an example. The controller to be developed has to minimise the waiting time of the public transportation while maintaining the individual traffic flowing optimally. First, the model of the chosen traffic crossing is derived. Then, using a combination of 'Dynamic Programming' and 'Branch and Bound' the control algorithm is presented. A visualisation of the algorithm is given by means of graphs, complexity issues are investigated, and computational refinements proposed. The actual implementation of the control algorithm for the example shown is under way and carried out in co-operation with the Transportation Authority of the city of Zurich. The work presented here is part of a bigger project. The overall goal is to provide the traffic engineer with a tool for designing 'intelligent' controllers for traffic lights.
This manual is directed to those who have previously acquired some programming skill. The intention is to provide a means of learning Pascal without outside guidance. It is based on The Programming Language Pascal (Revised Report) [1]--the basic definition of Pascal and concise reference manual for the experienced Pascal programmer.
The linear structure of a book is by no means ideal for introducing a language, whether it be a formal or natural one. Nevertheless, it is recommended to follow the given organization, paying particular attention to the example programs, and then to reread those sections causing difficulties. One may wish, however, to reference chapter 12 if troubles arise concerning the input and output conventions of the programs.
The manual was prepared as a file on a computer, that is, as a sequence of characters of a single type font. This is very convenient for the purposes of updating; unfortunately, it is sometimes a bit awkward to read. The reader is asked to be indulgent with the absence of sub- and superscripts (e.g. m raised to the power n is denoted by m**n).
Chapters 0--12 define the language Pascal and serve as a standard for both the implementor and the programmer. The implementor must regard the task of recognizing Standard Pascal as the minimum requirement of his system, while the programmer who intends his programs to be transferable from one installation to another should use only features described as Standard Pascal. On the other hand, any implementation may (and usually does) go beyond the minimum. Chapters 13 and 14 document the implementation of Pascal on the CDC 6000 machine. Chapter 13 describes the additional features of the language PASCAL 6000, whereas chapter 14 is devoted to the use of the compiler and the system under the operating system SCOPE.
A traffic signal progression program was developed that maximizes progression along a facility having multiphase signals. The main street green phase sequences of left turns first, through movements first, leading green, and lagging green can be evaluated at each intersection. The progression program can determine which of the four phase sequences provides maximum progression.
