快速路单双汇入匝道主线交通流运行分析

Analysis of Mainline Traffic Flow of Expressway Single-and Double-Parallel Entry Ramp

文章研究快速路单双平行式汇入匝道对快速路主线交通流运行状态的影响。借助微观交通仿真软件VISSIM,对不同交通需求情况下两种匝道形式的快速路汇入部分进行仿真,通过采集主线交通流的车速、延误、流量等数据,分析得出当主线和汇入流量的流量/通行能力比率(v/c)小于0.7时,单双平行式汇入匝道对主线交通流的运行状态的影响差别不大,且主线仍能保持较高的速度运行,此时选择匝道形式更多应考虑土地空间、建设成本等因素;当主线和汇入流量的v/c超过0.7时,单双平行式汇入匝道主线交通流车速波动呈现截然相反的情况,此时根据交通需求选择匝道形式对提高快速路运行效率有更重要的意义;当交通流趋于饱和流时,单双平行式汇入匝道在主线运行状态上差别不大。对主线三车道交通流车速—流量分析得出,双车道平行式汇入匝道,主线交通流呈现明显的自由流和拥堵流两级分化的局面,单车道平行式汇入匝道,主线交通流各状态过渡平缓。

This paper studied the effects of the single-and double-parallel entry ramp of expressway on the mainline traffic flow. Microscopic traffic simulation software VISSIM was used to simulate expressway import parts of the two ramps under different traffic demands. The analysis of such data as vehicle speed, delay and traffic flow from mainline traffic flow shows that when v/c of the main line and import flow is less than about 0.7,the single-and double-parallel entry ramp has little influence on the operation state of the mainline traffic flow,with the main line still maintaining high speed. In case of ramp forms, factors including land space, construction cost and other factors should be given more attention to. When v/c of the main line and import flow is more than about 0.7, vehicle speed fluctuations of the main line traffic flow of the single-and double-parallel entry ramp is the opposite of the present situation. So the choice of ramp forms in accordance with traffic demands is very important for improving the expressway operating efficiency; when the traffic flow approaches saturation, the singleand double-parallel entry ramps are not different in terms of the mainline operation state. The speed-flow analysis of mainline three-lane traffic flow shows that the mainline traffic flow presents obvious free flow and congestion flow regarding double-parallel entry ramp while the mainline traffic flow keeps steady regarding single-parallel transport ramp.