通道中行人-机动车相互作用机理的建模和模拟

本文研究了通道中行人与车辆同向或反向运动时的人车相互作用.车辆运动的描述采用细化的确定性元胞自动机模型,而行人流则采用考虑背景场的格子气模型.车辆及其影响区被视为一种可移动的障碍物,形成动态变化的背景场,可以更好地反映人车之间的相互作用.通过数值模拟得到典型参数下的行人流基本图以及平均车速随行人密度的变化曲线.人车反向时行人流基本图中存在两个临界密度,其间的行人流量-密度曲线呈线性分布,曲线斜率k主要依赖于车辆宽度和行人预判时间,而平均车速近似为k,即反向车辆形成的移动瓶颈和行人拥堵向上游传播的速度是一致的.文中进一步考察了行人预判时间、车辆宽度及限速对人车混合交通流的影响.人车同向时,这三个参数的影响都不明显.人车反向时,当车辆宽度较小,即使在很高密度下,车辆仍可以前行,而更大的行人预判时间也有助于车辆的运动.

Modeling and simulation on interaction between pedestrians and a vehicle in a channel

The mixed traffic flow composed of pedestrians and vehicles shows distinct features that a single kind of traffic flow does not have. In this paper, the motion of a vehicle is described by the finer deterministic Nagel-Schreckenberg model, while the motion of pedestrians is mimicked by the lattice gas model with taking the floor field into account. Then the interaction between a certain vehicle and pedestrians in a narrow channel is investigated in two cases, i.e., pedestrians move in the same as or opposite to the direction of vehicle. The direction of the pedestrian movement is determined by the floor field, and the vehicle (and its influential area), regarded as a movable obstacle, and thus causing the floor field to change. Because of the timely change of vehicle speed and the size of impact area, the floor field must be calculated at each time step. Through numerical simulation, the fundamental diagram for pedestrian flow under the typical parameters is obtained together with the average speed of the vehicle as a function of pedestrian density. It is found that there are two critical densities, i.e., ρ₁ and ρ₂. When ρ₁ ≤ ρ ≤ ρ₂, the fundamental diagrams in the two cases are significantly different. This is due to the reverse movement of pedestrian and vehicle, the congestion ahead of the vehicle makes the average speed of pedestrians significantly lowered. In this case, the flux of pedestrians is a linear function of pedestrian density, and its slope indicates the speed at which pedestrian congestion propagates upstream. It can also represent the speed of the moving bottleneck formed by the vehicle. The slope mainly depends on the width of the vehicle and the anticipation time of pedestrians. When ρ < ρ₁ and ρ > ρ₂, there is no obvious difference between the two cases. We further investigate the effect of three parameters, i.e., the anticipation time of pedestrians, the width and the speed limit of the vehicle. When pedestrians have the same direction as the vehicle, these parameters only have negligible effects. However, in the case that pedestrians move oppositely to the vehicle, the width of the vehicle influences the mixed traffic significantly. When the width of the vehicle is small, even in rather high pedestrian density, the vehicle can move forward. In addition, larger anticipation time of pedestrians is helpful in improving the speed of vehicle, while the effect of the speed limit of vehicle is relatively small. The spatial distribution of pedestrians and the vehicle and the short time average speed of the vehicle are also provided to reveal more information about both pedestrians and the vehicle.