A Fourier Perspective of Freeway Traffic

This paper presents the Simulator of Intelligent Transportation Systems (SITS) and a dynamical analysis of several traffic phenomena. The SITS is based on a microscopic simulation approach to reproduce real traffic and considers different types of vehicles, drivers and roads. In order to process the resulting information, it is also introduced a new modelling scheme based on the embedding of statistics and Fourier transform. The results point out that it is possible to study traffic systems, taking advantage on the knowledge gathered with systems theory. INTRODUCTION Nowadays we have a saturation of the transportation infrastructures due to the growing number of vehicles over the last five decades. This situation affects substantially our lives, while people needs, more and more, to move rapidly between different places. The results are traffic congestion, accidents, transportation delays and larger vehicle pollution emissions. The difficulties concerned with this subject motivated the research community to center their attention in the area of ITS (Intelligent Transportation Systems). ITS applies advanced communication, information and electronics technology to solve transportation problems such as, traffic congestion, safety, transport efficiency and environmental conservation. Therefore, we can say that the purpose of ITS is to take advantage of the appropriate technologies to create “more intelligent” roads, vehicles and users [1-2-3]. 2 Computer simulation has become a common tool in the evaluation and development of ITS. The advantages of this tool are obvious. The simulation models can satisfy a wide range of requirements, such as: evaluating alternative treatments, testing new designs, training personal and analyzing safety aspects [4-5]. Bearing these facts in mind, this paper is organized as follows. Section 2 describes briefly the microsimulation model SITS. Section 3 presents simulation results related with the dynamic behaviour of a traffic system. Finally, section 4 presents some conclusions and outlines the perspectives towards future research. THE SITS SIMULATION PACKAGE SITS is a software tool based on a microscopic simulation approach, which reproduces real traffic conditions in an urban or non-urban network. The program provides a detailed modelling of the traffic network, distinguishing between different types of vehicles and drivers, and considering a wide range of network geometries. SITS uses a flexible structure that allows the integration of simulation facilities for any of the ITS related areas. This new simulation package is an object-oriented implementation written in C++. The overall model structure is represented on Figure 1. SITS Overall Model Structure Graphical User interface (GUI) Traffic Control Variable Speed Limit Ramp Metering Traffic Control signal Printouts Measurements and Statistics Vehicle Data Driver Decision Surrounding environment Lane change Logic Driver Regime Route Geometry State-Oriented Modelling (SOM) Figure 1. SITS overall model structure SITS models each vehicle as a separate entity in the network according to the state diagram showing in figure 2. Therefore, are defined five states {1-aceleration, 2-braking, 3-cruise speed, 4-stopped, 5-collision} that represent the possible vehicle states in a traffic systems.