Experimental properties of phase transitions in traffic flow

Investigations of a great number of measurements of traffic flow on German highways show that there are some common macroscopic properties of phase transitions between free flow, synchronized flow, and traffic jams. In particular, it is shown that a short-time localized perturbation is able to cause a local phase transition from free flow to synchronized flow and that synchronized flow of slow moving vehicles can further be self-maintained on a highway for several hours.