Now casting of traffic state by GPS data. The metropolitan area of Rome

In the near future a large amount of data on individual vehicle position and speed for the full road network will be available from GPS systems. This possibility opens new research perspectives for prevention and governance of congestion and of traffic criticalities. A prototype model, developed under Pegasus Project sponsored by the Italian Ministry of Industry, is working in Rome. The system is based on the real time reconstruction of the speed, density and flux on the whole metropolitan road network using a low sampling rate GPS data set. We present the state of the art of the project discussing its strength and weakness. We then show the results of the data analysis for the month of May 2010.