Models And Simulations Of Road Traffic Flow Based On The Modified Weighted Probabilistic Cellular Automaton

In real traffic circumstances, there exist various vehicle types and driving styles. Thus a driver mostly reacts differently from others even to the same traffic situation due to the diversity of vehicle performance and drivers' personality. Besides, noises or disturbances also affect driving behaviors. These factors may cause complex traffic phenomena. On the other hand, bottlenecks also play an important role in influence the traffic. Traffic jams, synchronized flow and many other complicated traffic phenomena are observed near the bottlenecks. The homogeneous and stable free traffic flow is usually disturbed and evolves into different congested traffic patterns, when it arrives at a bottleneck. However, the various and complex traffic phenomena induced by the bottlenecks are still not well understood, and the mechanisms of them need to be further investigated and discussed. Especially, on-ramp in city highway is one of the most typical bottlenecks. In this paper, a modified weighted probabilistic cellular automaton model is proposed, in which the effects of the velocity at last time step was taken into account. Based on the proposed model, an on-ramp system is simulated. The traffic behaviors near the on-ramp are analyzed and the influence of conformity effect on traffic characteristic of the on-ramp system is discussed. The main contents of the paper are follows:1. In real traffic, a vehicle's velocity can't change abruptly in two successive time steps. Because of the continuity of driving, a vehicle's velocity at the next time is not independent of that at the current time. On the contrary, the former is obtained by accelerating or decelerating on the basis of the latter. The continuity of velocity wasn't considered in the previous researches. Considering the continuity of velocity, a modified weighted probabilistic cellular automaton model is proposed in this paper. Simulation results show that the model is able to reproduce the characteristics of synchronized flow. Consequently, it is suggested that the diversity of drivers and vehicles may result in the appearance of synchronized flow.2. Based on the modified weighted probabilistic cellular automaton model presented above, simulation and investigation are launched to study traffic patterns at the locations of on-ramp traffic bottleneck. After a series of analysis of relevant phase diagram and spatiotemporal diagrams, it is pointed out that traffic patterns at the locations of on-ramp traffic bottleneck are well reproduced. 3. The traffic system with two-lane main road and one-lane on-ramp is simulated and analyzed, using the presented modified weighted probabilistic cellular automaton model. The conformity effect of the vehicles on the ramp is considered. The phase diagrams considering and not considering the conformity effect are analyzed and compared to study the influence of conformity effect on traffic flow characteristics. The variations of the capacity at upstream the on-ramp, the on-ramp and downstream the on-ramp with respect to the conformity probability is analyzed, when main road and on-ramp both are saturated. The results indicate that conformity effect can weaken the bottlenecks effect caused by the main road on the on-ramp to some extent and increase capacity of on-ramp.