  Recently, a phase transition to synchronized congested traffic has been
observed in empirical highway data [B. S. Kerner and H. Rehborn, Phys. Rev.
Lett. 79, 4030 (1997)]. This hysteretic transition has been described by a
non-local, gas-kinetic-based traffic model [D. Helbing and M. Treiber, Phys.
Rev. Lett. 81, 3042 (1998)] that, however, did not display the wide scattering
of synchronized states. Here, it is shown that the latter can be reproduced by
a mixture of different vehicle types like cars and trucks. The simulation
results are in good agreement with Dutch highway data.

Statistical Mechanics