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In this paper a traffic assignment model is specified in road emergency conditions. The proposed model takes into account two classes of users: some users in emergency conditions repeat the same choice made in ordinary conditions, some others make a different choice. The basic concept for the proposed model is derived from day-today models. The path choice model, which is inside the traffic assignment model, has to take into account three types of information which influence users' choices: historical information related to network experience in ordinary conditions, real time information related to the current emergency situation, and users' forecasting of the network evolution based on current experience. A non-equilibrium dynamic model is adopted in order to simulate path flows on the network. A review of static and dynamic traffic assignment models in emergency conditions is reported.

The paper focuses on Intelligent Transport Systems (ITS) oriented to route choice management and control on urban road transportation networks. The elements of an ITS may be grouped into three functional classes: survey and transmission, control and users information. ITS for survey require an architecture based on sensors located on the network, which detect traffic conditions. ITS for control have their core in the so-called Decision Support Systems (DSS), which may operate both in ordinary and emergency conditions. Emergencies in transport system require a real-time management in order to support decision makers in a dynamic context. ITS for users information allowing dissemination of information to users during their trip. Information may be descriptive or prescriptive in relation to the management strategy adopted. In the paper the description of each functional class considers hardware and software elements.

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