高速公路坡道对交通流的影响

采用周期边界条件,建立单车道不同路段最大速度不同的元胞自动机交通流模型,模拟研究坡道长度、坡道倾度、较慢车混合比例和增设爬坡道对高速公路交通流的影响。结果表明,坡道长度不同时,车辆的临界密度相同,车辆达到临界密度之前的平均速度随坡道长度的增加而减小,在中等密度区域对应的交通流量随坡道长度的增大而减小;坡道倾度增大时,车辆平均速度明显减小,相应的车辆临界密度也减小,在中等密度区域内的最大流量随着坡道倾度增大而迅速减小;只要有较慢车存在,不同较慢车的混合比例对交通流的影响基本相同;增设爬坡道前后车辆的临界密度相同,增设爬坡道后的车辆平均速度比没有爬坡道时大,密度不是特别大时,增设爬坡道可以大大提高高速公路的通行能力。

The Effect of Uphill Gradient Bottleneck on Freeway Traffic

Considering the different maximum speed of vehicles run on different road sections,we present a Cellular Automaton model for single-lane vehicle traffic flow under the periodical boundary condition.We study the effects of uphill gradient and after setting up the uphill-climbed gradient lane on freeway traffic.The results indicate that the critical density of traffic flow is the same with different slope length.Before the critical density,the average speed decreases with the increasing of the slope length.In the moderate density rigion,the traffic flow decreases a little with the increasing of the slope length;When the dumping of slpoe increase,the average speed decreases greatly even in free flow,the corresponding critical density decreases too.After the critical point,the speed decreases greatly with the increasing of the slope dumping.All the speeds are not the same untill the density is large enough.In the moderate density rigion,the max traffic flow decreases soon with the increasing of the slope dumping,and the proportion of slower vehicles have no strong influence on the traffic flow;the critical density of traffic flow is not changed after setting up another uphill gradient.Before the critical point,when set up the uphill-climbed gradient,the speed decreases soon with the increasing of the density,but it is bigger.After the critical point,when the density is not large enough,the speed is still bigger.The speed in the two condictions are not the same untill the density large enough.