Identifying the Impact of Low-Speed Vehicles on Freeway Capacity by Traffic Simulation

It is agreed that freeway has higher capacity than urban streets because of its higher speed limits and relatively closed traffic condition. However, the existence of low-speed vehicles on freeways, as well as resultant frequent lane-change and overtaking behaviors of other vehicles, will greatly decrease the capacity. And low-speed fines have been imposed on some freeways in China. In order to further clarify the impact of the characteristics of low-speed vehicles (i.e., speed, proportion, and driving lanes) on traffic capacity and overall traffic state, in this paper we conduct extensive simulation experiments using VISSIM 11 software. Different demand levels and freeways with different number of lanes are constructed by VISSIM to obtain comprehensive results under diverse proportion of low-speed vehicles. This study can help analyzing the impact of vehicle speed composition on traffic state, as well as providing guidance for the formulation and application of relevant traffic policies.