Study On Single Lane Traffic Flow Model Based On Cellular Automata

Transportation system is a complex system including human, vehicle, road, which hasmacroscopic characteristics on the whole as well as has individual differences and certainrandomness among the internal factors. These characteristics have very similar characteristicsas those of cellular automata. Therefore, in this thesis, the theory of cellular automata isintroduced into traffic flow field, through modeling and simulation of microscopic traffic flow,to reveal the inherent characteristics and evolution mechanism.Combined the Nagel-Schreckenberg single lane cellular automaton model (NS model)with the relationship of speed, density, volume, a one-dimensional cellular automaton singlelane microscopic traffic flow model considering the single vehicle speed affected by trafficflow density is established in the thesis. With the real-time change of single lane traffic flowdensity, the model can adaptively determine the roads in which traffic state--free flow,metastable, or a congested state. The new speed updating rule is proposed for the three trafficflow states, and introducing slow start on all vehicles with zero speed.In the free flow state, since the vehicle is less affected by noise, the one problem in NSmodel is solved which the simulation speed is less than the actual speed through estimatingthe previous vehicle’s speed. In other states, the model can reduce the vehicle speed and easedthe traffic congestion after we improved randomization rules. This model helps to improve thesimulation of traffic volume, and shows a more real single lane traffic flow.We did computer simulation with Matlab, and achieved vehicle`s time/space diagrams.The results show that the model can better reproduce the the single lane free flow, metastable,or a congestion diffusion phenomena. Compared to NS model and VE model, the model has asignificant improvement for the average traffic flow speed and the traffic volume in the flowstate and other states. The model has great significance to study on single-lane traffic flowcharacteristics, and is helpful to further study on the traffic jams.