Dong Li-Yun

The Effect of the Relative Velocity on Traffic Flow

The optimal velocity model of traffic is extended to take the relative velocity into account. The traffic behavior is investigated numerically and analytically with this model. It is shown that the car interaction with the relative velocity can effect the stability of the traffic flow and raise critical density. The jamming transition between the freely moving and jamming phases is investigated with the linear stability analysis and nonlinear perturbation methods. The traffic jam is described by the kink solution of the modified Korteweg–de Vries equation. The theoretical result is in good agreement with the simulation.

One-dimensional cellular automation model of traffic flow based on car-following idea

An improved one-dimensional CA (Cellular Automaton) traffic model was proposed to describe the highway traffic under the periodic boundary conditions. This model was based on the idea of the car-following model, which claims that the motion of a vehicle at one time step depends on both its headway and the synchronous motion of the front vehicle, thus including indirectly the influence of its sub-neighboring vehicle. In addition, the socalled safety distance was introduced to consider the deceleration behavior of vehicles and the stochastic factor was taken into account by introducing the deceleration probability. Meanwhile, the conditional deceleration in the model gives a better description of the phenomena observed on highways. It is found that there exists the metastability and hysteresis effect of traffic flow in the neighborhood of critical density under different initial conditions. Since this model gives a reasonable depiction of the motion of a single vehicle, it is easy to be extended to the case of traffic flow under the control of traffic lights in cities.

An improved cellular automaton model considering the effect of traffic lights and driving behaviour

This paper proposes an improved cellular automaton model to describe the urban tra‐c ∞ow with the consideration of tra‐c light and driving behaviour efiects. Based on the model, the characteristics of the urban tra‐c ∞ow on a singlelane road are investigated under three difierent control strategies, i.e., the synchronized, the green wave and the random strategies. The fundamental diagrams and time-space patterns of the tra‐c ∞ows are provided for these strategies respectively. It flnds that the dynamical transition to the congested ∞ow appears when the vehicle density is higher than a critical level. The saturated ∞ow is less dependent on the cycle time and the strategies of the tra‐c light control, while the critical vehicle density varies with the cycle time and the strategies. Simulated results indicate that the green wave strategy is proven to be the most efiective one among the above three control strategies.

Dynamic characteristics and simulation of traffic flow with slope

This paper proposes a new traffic model to describe traffic flow with slope under consideration of the gravity effect. Based on the model, stability analysis is conducted and a numerical simulation is performed to explore the characteristics of the traffic flow with slope. The result shows that the perturbation of the system is an inherent one, which is induced by the slope. In addition, the hysteresis loop is represented through plotting the figure of velocity against headway and highly depends on the slope angle. The kinematic wave at high density is also obtained through reproducing the phenomenon of stop-and-go traffic, which is significant to explore the phase transition of traffic flow and the evolution of traffic congestion.

Self-organized phenomena of pedestrian counter flow in a channel under periodic boundary conditions

In this paper we investigate self-organized phenomena such as lane formation generated by pedestrian counter flow in a channel. The lattice gas model is extended to take the effect of walkers in the opposite direction into account simultaneously when they are in the view field of a walker, i.e., walkers tend to follow the leaders in the same direction and avoid conflicts with those walking towards them. The improved model is then used to mimic pedestrian counter flow in a channel under periodic boundary conditions. Numerical simulations show that lane formation is well reproduced, and this process is rather rapid which coincides with real pedestrian traffic. The average velocity and critical density are found to increase to some degree with the consideration of view field.

Simulation of traffic flow with traffic light strategies via a modified cellular automaton model

Traffic flows controlled by traffic light strategies were investigated via a cellular automaton model with anticipation, which is suitable for describing urban traffic. Three kinds of strategies, i.e., synchronized, green-wave and random switching lights, were designed, simulated and compared with each other. It is shown that the green-wave strategy is only valid at lower density and there is not an effective way with the three strategies to improve the efficiency of traffic flow at high density.

Effect of relative velocity on the optimal velocity model

In this letter, an unproved optimal velocity model was proposed that assumes die effect of relative velocity deceases with the increment of gap between successive cars. Numerical simulation was carried out to test whether this model could depict the braking process correctly. The simulation results show good agreement with observed data.

Jam Formation of Traffic Flow in Harbor Tunnel

This paper reports a study concerning occurrence and growth of traffic jam in a harbor tunnel. The single-lane with three sections (downgrade, flat, and upgrade) is taken into account and they are characterized with different velocity limit. At the low density, the traffic current increases linearly with density and saturates at some values of immediately density. As the density increases, the traffic jam appears firstly before the upgrade section and then extends to the downgrade section. Additionally, the relationships of the velocity and headway against position in different densities are obtained from simulation. These results clearly clarify where and when the traffic jam appears. Finally, the critical densities are derived via the theoretical analysis before and after the discontinuous fronts and the theoretical results are consistent with the critical values of simulation results.

The density wave in a new anisotropic continuum model

In this paper the new continuum traffic flow model proposed by Jiang et al is developed based on an improved car-following model, in which the speed gradient term replaces the density gradient term in the equation of motion. It overcomes the wrong-way travel which exists in many high-order continuum models. Based on the continuum version of car-following model, the condition for stable traffic flow is derived. Nonlinear analysis shows that the density fluctuation in traffic flow induces a variety of density waves. Near the onset of instability, a small disturbance could lead to solitons determined by the Korteweg–de-Vries (KdV) equation, and the soliton solution is derived.

A Modified Sensitive Driving Cellular Automaton Model

A modified cellular automaton model for traffic flow on highway is proposed with a novel concept about the variable security gap. The concept is first introduced into the original Nagel–Schreckenberg model, which is called the non-sensitive driving cellular automaton model. And then it is incorporated with a sensitive driving NaSch model, in which the randomization brake is arranged before the deterministic deceleration. A parameter related to the variable security gap is determined through simulation. Comparison of the simulation results indicates that the variable security gap has different influence on the two models. The fundamental diagram obtained by simulation with the modified sensitive driving NaSch model shows that the maximum flow are in good agreement with the observed data, indicating that the presented model is more reasonable and realistic.