Estimation of freeway traffic variables using information from mobile phones

The presence of mobile phones on a freeway can be exploited to provide information on the traffic behavior. To this end, an extension of a standard freeway macroscopic model is presented that allows to describe the dynamic of the overall cars, together with variables representing the percentage of communicating mobile phones. A freeway trunk is divided into sections, each covered by a cell of the wireless network and associated with state variables describing density of vehicles, mean velocity, and percentage of active mobile phones. The measurements of mobile phone densities in the various cells of the network are used to estimate these state variables using an extended Kalman filter. A complex simulation set-up has been developed for the purpose of validation. Simulation results are reported to show the effectiveness and potential of the proposed approach.