Research Of Critical Characteristics Of Mixed Traffic Flow Of Freeway

In recent years, the research of traffic flow theory has been widely concerned at home and abroad. Through the establishment of the traffic flow model which is in line with the general characteristics of the real road traffic, the inherent rule of the traffic flow can be effectively revealed. By analyzing the characteristics of the elements of the traffic system,giving a reasonable explanation of the relation among the three traffic flow parameters, and solving the traffic bottlenecks, congestion, and critical problems, one can plan road traffic facilities more better, make effective security control measures, improve traffic capacity,achieve efficient using of road resources. Therefore, a comprehensive investigation on traffic flow theory is of great significance.The main contents of this paper are as follows:Firstly, the research methods and ideas are inspired by tracing the relevant results on the critical characteristics of the mixed traffic flow at home and abroad. After a large collection and reading of relevant research results, this paper analyzes and expounds the hot topics and existing problems in the traffic flow theory, and clarifies the significance of the research on the traffic flow theory. This paper discusses the definition and classification of mixed traffic flow, analyzes the relationship among the three traffic flow parameters, and sums up the phenomena and characteristics of traffic measurement based on the theory of basic graph theory and three-phase flow. At the same time, this paper introduces the cellular automaton(CA) model and related theories, and summarizes the current main applications in the field of road traffic.Secondly, through improving the NS model, the periodic boundary conditions of single lane mixed traffic flow model are established. This paper discusses the influence of the vehicle mix proportions and random slowing change on traffic flow. Several simulation results show that mixing ratio has larger effects on the flow and speed of hybrid vehicle traffic on single lane. The average velocity and flow of mixed traffic flow decrease overall when the proportion of carts increases. Similarly, the random deceleration probability P of vehicle plays an important role on the speed, traffic and motion state of hybrid vehicle. The critical density of the overall traffic decreases as the random deceleration value P increases.Then, considering into the fact that the speed of following vehicles is different with that of the vehicle in front, this paper improves the acceleration and deceleration rules in the process of the traffic flow evolution. In this paper, the vehicle acceleration is no longer a fixed value, and the random deceleration probability depends on the speed of the vehicles before and after. Based on which, the single lane CA model is established with the velocity difference considered. Through simulation, characteristics of the three parameters of trafficflow are obtained, which are different with the fundamental diagram of the traditional NS model, the overall traffic speed and flow of the former are larger. At the same time, by introducing the effect of expected velocity, the influence of different randomization deceleration rates on traffic flow is analyzed. Simulation results show that the introduction of expected speed controls the high speed vehicles effectively, and the overall traffic speed decreases slowly as the density increases. Therefore, the simulation results of the traffic flow model based on the velocity difference shows that the impact of acceleration and deceleration of vehicles on the state of overall traffic flow, that is, the critical density of the road is larger.Finally, in order to further explore the complex mechanism of vehicles and characteristics of traffic congestion in the ramp bottleneck, the VDE model under the three phase traffic flow theory is established in the paper. Theoretical analysis of this model is demonstrated, different congestion patterns in the on-ramp bottleneck are simulated using the model, and traffic congestion propagation and critical phase transition are discussed from macroscopic and microscopic aspects. Moreover, the congestion patterns under the mutual interference of two kinds of combined ramp traffic flow and the corresponding parameters are discussed, the traffic characteristics of the combined ramp and isolated on-ramp are comparative analyzed, and the statistics of flow and speed of the local traffic on the upstream and downstream of the ramp under different main flow conditions are got. The traffic changing rules which conform to reality are obtained through theoretical analysis combined with the actual situation.