Towards a non-equilibrium statistical physics for mobility on road networks
Description
New communication technologies allow to record dynamical microscopic data on large social systems. Even if the population samples are still limited, the situation if quickly improving. In Italy single vehicle trajectories are monitored by a GPS system for insurance reason. The data concern 2% of the whole vehicle population and the trajectories are sampled at a spatial scale of 2 Km. But we have information on time, positions, instantaneous velocity, covered distance and signal quality; moreover the starting and ending points of each trajectories are recorded. Recent studies of Florence urban area[A.Bazzani et al, Statistical Laws in Urban Mobility from microscopic GPS data in the area of Florence, submitted for publication 2009] have pointed out that in the average the GPS data represent an urban mobility that can be described by an ergodic principle based on the existence of a mobility energy for the daily mobility paths and by a Benford law for the activity downtime distribution. To enrol the system complexity is then necessary to study transient states out of equilibrium, like, for instance, the rise of congestion phenomena in a road network. The GPS data base is not enough detailed to study congestion phenomena in a urban road network, but it can be suitable to detect congestion evolution on larger scale road networks (like an italian region). In this work we analyze the GPS data recorded on the whole Emilia-Romagna region during November 2007 to look for congestion effects and their evolution. We propose to describe the congestion dynamics by using the instant velocity and the trajectories of the monitored vehicles. We consider also the behavior of some selected drivers that are used to move in the considered area. Our aim is to define analytical instruments able to detect and to follow congestion evolution by means of real-time microscopic data, in order to perform a nowcasting approach to govern criticalities.
Organised by Vito Latora