Strategies for signal settings and dynamic traffic modelling

The paper describes the objectives, the methodology and the preliminary results of the research project “Interaction between signal settings and traffic flow patterns on road networks”, granted by the Italian Ministry of University and Research with the Fund for Investments on Basic Research (FIRB). The project joins three research units, belonging respectively to the University of Rome “La Sapienza”, the University “Roma Tre” and the Institute for Information System Analysis (IASI) of the Italian National Council of Research. The object of the research is to develop a general procedure to study, model and solve the problem of optimal road network signal settings, by taking into account the interaction between signal control systems and traffic flow patterns. This problem is interesting by both a theoretical and an application point of view, since several mathematical studies and experimental results have shown that usual signal setting policies, which simply adjust signal parameters according to the measured traffic, may lead to system unstable solutions and deteriorate network performances. At core of the problem is the difference between a user equilibrium flow pattern, where individuals choose their paths in order to minimize their own travel time, and a system optimizing flow that minimizes total delay of all users. The problem is object of an intensive research activity by the scientific community by many years (Cfr. [3] and [19]). The global optimal signal settings on a road network is a complex problem that involves dynamic traffic patterns, users’ route choice and real-time application of suitable control strategies. With several noticeable exceptions (Cfr. [13], [18], [1] and [2]), the problem is usually tackled by following an equilibrium approach, that is, by searching for a possibly optimal configuration of mutually consistent traffic flows and signal variables (Cfr. [5]). In order to investigate real-time applications, the research project aims at extending the static modeling framework usually adopted in the scientific literature to apply dynamic traffic assignment models and deal with both coordinated arteries and traffic-flow responsive signal settings. The study is being developed focusing on the following topics: • Modelling of traffic flow along coordinated traffic networks and real-time applications of synchronization strategies; • Advanced models and methods for signal settings and traffic control.