1 Real-time traffic monitoring and forecast through OPTIMA - Optimal Path Travel Information for Mobility Actions Lorenzo Meschini 1 , Guido Gentile 1 Abstract OPTIMA is an innovative ITS (Intelligent Transport Systems) platform for traf- fic monitoring and management, that provides off-line estimates and real-time fore- casts concerning the use (vehicle flows) and the performances (travel times) of the road networks. To this end, OPTIMA exploits an advanced methodology for modelling transport demand and vehicle congestion, through which the behaviour of drivers and the propagation of queues are explicitly represented. The connection to actual conditions is guarantied by field measures at discrete points (loop detectors, speed radars, video cameras, probe vehicles) that are collected in real-time and sent to a control room, where sophisticated algorithms allow to reconstruct the current and future traffic pat- tern on the entire network, hence extending the available data in time and space to achieve a useful information for driver navigation and transport optimization. 1. Introduction 1.1 Overview of the technology OPTIMA relies on a priori estimations of the traffic evolution during each day-type that are accomplished through the simulation of the whole transportation system, which reproduces the path choices of drivers travel- ling on the congested road network from their origin to their destination at specific instants. Then, the real-time measures are used to calibrate and cor- rect such a mobility model, adjusting the base estimation to the current traf- fic conditions, thus providing a very robust and reliable prediction. Our approach, primarily based on the physical interpretation of the traffic phenomena, differs substantially from the mere interpolation of field meas- ures through artificial intelligence methods. Most monitoring systems apply, 1 Dipartimento di Idraulica Trasporti e Strade, Sapienza Università di Roma