Research On A Cellular Automata Traffic Flow Model For Three-phase Theory

In early researches of the traffic flow theory,the fundamental diagram approach had remained as a dominant theory.Models which are based on the fundamental diagram approach could be divided into three categories,namely,the macroscopic,the meso-scopic,and the microscopic ones.Although lots of phenomena in real traffic state could be simulated by models based on the fundamental diagram approach,such as the go-and-stop phenomenon and the propagations of nonlinear traffic waves,the real traffic state could not be revealed perfectly by the fundamental diagram approach.In the congested traffic condition,the empirical observations showed that flow-density data are distributed in a 2D region.Anyway,the average flow rate,which was the product of the average speed and the density,was a function of the density which had a maximum.The curve in the flow-density plane was called the fundamental diagram,which was the basis of the fundamental diagram approach.So the fundamental diagram approach failed to cover the overall situation of the traffic flow.Hypotheses of Kerner's three-phase theory have been firstly formulated in 1998 and further developed later.A history of the emergence of Kerner ' s three-phase theory can be found in the review by Rehborn and Klenov as well as in papers by Rehborn,Klenov et al..In Kerner's three-phase theory,the traffic flow had been divided into three phases: 1.free flow phase(F),2.synchronized flow phase(S)and 3.wide moving jam phase(J).The F ? S transition is caused by the traffic breakdown,and the instability leads to the S ? J transition.The view on synchronized flow was the main difference between the fundamental diagram approach and the three-phase traffic flow theory.In the opinion of the fundamental diagram approach,synchronized flow was a transient state.However,synchronized flow was a stable intermediate state in the three-phase traffic flow theory.It's revealed the microscopic features of traffic breakdown at the on-ramp bottleneck in the real traffic.We found that the disturbance caused by the preceding car can propagate upstream of the bottleneck.However,the traffic breakdown does not occur only at the bottleneck;It also occurs due to the disturbance of speed decrease.In order to analyze the propagation of the speed disturbance on the mainroad of a highway in the free flow and the synchronized flow,this paper presents a newly-modified KKW model by taking some drivers' s behavior into consideration.