The Micro Modelling And Simulation Of The Complex Properties Of Traffic Flow

ABSTRACT:Recent years have witnessed a substantial development in traffic flow theory. A large number of traffic models have been proposed by scientists. Generally speaking, there are two types of traffic models:microscopic and macroscopic models. Macroscopic models regard the whole traffic flow as a flow of continuous medium based upon a continuum approach. Microscopic models, including the car-following models and cellular automata models, pay attention to each individual vehicle. In this paper, we focus on the car-following models and the cellular automata models in the framework of Kerner's three-phase traffic theory. Cellular automata models with flexible rules not only can reproduce the non-linear characteristics of complex traffic systems, but also are suitable for rapid computer simulations. Car-following models describe the motion of vehicles following each other on a single lane. These models have been used by many scientists and in traffic engineering. The three-phase traffic theory also has been used in traffic control. The work of this paper is as follows.1. Based on the MCD model in the framework of Kerner's three-phase traffic theory, we developed a new cellular model called the brake light model with considering the difference in accelerating and decelerating performance under different driving conditions (BL-DAD model). The simulation results show the following two important features:(1) The decelerating difference is the main reason for making the new model reproduce the synchronized flow, because if we remove the decelerating difference, the synchronized flow will disappear; (2) Accelerating difference has a little influence on the reproduction of the synchronized flow, but strong influence on the maximum of the flux.2. According to the BL-DAD model presented above, simulation and investigation work is launched to study traffic flow patterns at the locations of on-ramp system. After a series of analysis of relevant spatiotemporal diagrams, it is pointed out that the BL-DAD model could reproduce lots of traffic phenomena under the on-ramp system. But the first order transition from free flow to synchronized flow and moving synchronized flow couldn't be reproduced by BL-DAD model. Therefore, based on BL-DAD model, we presented the FBL-DAD model, where'F'means the first order transition from free flow to synchronized flow. Simulation results show that FBL-DAD model could successfully reproduced the observed traffic phenomena in the framework of three-phase traffic theory.3. We improved the full velocity difference model by introducing velocity anticipation. Velocity anticipation means the follower estimates the future velocity of the leader. The stability condition of the new model is obtained by using the linear stability theory. Theoretical results show that the stability region increases when we increase the anticipation time interval. Numerical simulations exhibit that when we increase the anticipation time interval enough, the new model could avoid accidents under urgent braking cases. Also, the traffic jam could be suppressed by considering the anticipation velocity. Then through the nonlinear analysis, the Burgers, Korteweg-de Vries (KdV) and modified KdV (mKdV) equations are derived for the triangular shock wave, the soliton wave and the kink-antikink wave. At the same time, numerical simulations are also carried out to show that the model could simulate these density waves.