基于BPR函数的道路阻抗研究

A Study of Road Traffic Impedance Based on BPR Function

道路阻抗函数能够反映交通现状与通行时间的关系,如何准确确定道路阻抗是交通分配中急需解决的问题之一.美国公路局BPR(Bureau of Public Roads)函数是研究路段阻抗的基础,在分析探讨BPR函数作为道路阻抗的不足之后,对自由行驶时间与饱和度进行了修正,并考虑交通拥堵的存在,以提高BPR函数的实用性.基于大连市交通流实测数据,采用非线性回归模型计算改进BPR函数,分别对大连市的快速路、主干路、次干路和支路进行了参数标定.对比分析不同道路类型的标定结果,验证了考虑交通拥堵的改进BPR函数的正确性,最终得到的改进BPR函数能更好地反映大连市道路阻抗.

Road traffic impedance function can reflect the relationship between traffic situations and travel time. Thus, accurate calculation of road impedance is one of the urgent problems in traffic assignment. The research into road traffic impedance rests on the U.S. BPR （ Bureau of Public Roads） function. This paper begins with the examination of flaws of the BPR function and proposes approaches to improving travel time at free flow and saturation. Furthermore, to make the function more pragmatic, traffic congestion should be taken into consideration. Based on the real data of traffic flow collected in Dalian City, the BPR function calculated and improved by using nonlinear regression model is adopted to calibrate the parameters of fast-ways, trunk roads, secondary trunk roads and slip roads in Dalian City. The improved BPR function which takes account of traffic congestion is proved effective by the comparative analysis of the calibration for different road types. The function is also an indicator of road traffic impedance of Dalian City.