Traffic Flow States in a Freeway with Bottleneck

The system of mixture of single lane and double lane is studied by a cellular automata model, which isdeveloped by us based on the Nagel and Schreckenberg’s models. We justify that the model can reach a stable statesquickly. The density distributions of the stable state is presented for several causes, which illustrate the manner of thecongestion. The relationship between the outflow rate and the total number of vehicles and that between the outflowrate and the density just before the bottleneck are both given. Comparing with the relationship that occurring in thegranular flow, we conclude that the transition from the free traffic flow to the congested traffic flow can also be attributedto the abrupt variation through unstable flow state, which can naturally explain the discontinuities and the complextime variation behavior observed in the traffic flow experiments.