Density Waves and Jamming Transition in Cellular Automaton Models for   Traffic Flow
  In this paper computer simulation results of higher order density correlation for cellular automaton models of traffic flow are presented. The examinations show the jamming transition as a function of both the density and the magnitude of noise and allow to calculate the velocity of upstream moving jams. This velocity is independent of the density and decreases with growing noise. The point of maximum flow in the fundamental diagram determines its value. For that it is not necessary to define explicitly jams in the language of the selected model, but only based upon the well defined characteristic density profiles along the line. 
L. Neubert, H.Y. Lee, M. Schreckenberg