This M.Sc. thesis is focused on ITS for road transport, in particular on highways and motorways, from their origins to present applications. Their recent history makes them partially framed on an Italian and European legislative framework. The general architecture of communications between ITS is introduced, in particular the information sent to users by the infrastructure and vice versa. Subsequently, chapters concerning the automatic identification of road accidents are elaborated through the recall of specific algorithms, such as the well-dated California algorithm, developed in the late 1980s up, to most recent applications where a more capillary and detailed sensing of flows running on motorways or on highways can be pursued.