科研之友
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摘要
Previous studies have focused mostly on static passenger car equivalent (PCE) and showed that static PCE cannot accurately describe the interaction among vehicles in a crowded state. They did not consider the influence of the dynamic interaction among vehicles in different traffic states. To estimate the PCE according to the traffic state of a network dynamically, this study employed a macroscopic fundamental diagram (MFD) to analyze its sensitivity to the proportion of heavy goods vehicles (HGVs) on roads based on the checkerboard road network. This study also proposed a method to calculate the PCE of HGVs under various traffic states. First, the road network simulation model was constructed and the MFD was defined and verified using microscopic simulation. Secondly, the MFD of the network was modeled using a piecewise linear function according to simulation data, and multi-group simulation experiments were designed with changes in the proportion of large cars. Changes in the MFD shape along with various proportions of HGVs were studied. The sensitivity of the MFD to HGV proportion was analyzed qualitatively and quantitatively. Third, a method to estimate the PCE of HGVs under different typical traffic states based on the MFD was presented. The proposed PCE formulation indicates that the PCEs of HGVs are related to the proportion of HGVs under uncongested conditions, which corresponds to the rising section and continuous section of the MFD curve. When it is related to the number of vehicles in the network (or density) under congestion, it corresponds to the falling section. The method and insights proposed in this paper provide an understanding of HGV influence on the network traffic state, as well as provide support to transport planning and operation.
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