山区双车道公路运行速度预测模型的加速度标定

为标定运行速度模型中的汽车加速度值,在山区双车道公路上开展小客车连续行驶实验,采集轴向加速度的连续数据,并通过断面观测得到大客车和大货车的加速度值,获得峰值加速度的累积频率曲线以及统计分布特性,并建立加速度-道路几何参数关系模型.结果表明:小客车的入弯减速度幅值要比出弯加速度高一倍左右,不宜将加、减速度简化成同一个值,应该分别进行标定;加速度和减速度累积频率曲线的斜率突变点都不是发生在85~(th)百分位,而是临近95~(th),应重新考虑85~(th)百分位的使用价值;大客车的加、减速度幅值非常接近,而重载货车的减速度要明显大于加速度,同时,重载货车的加速度和减速度值要双双低于大型客车;小客车的加速度与弯道半径负相关,而与弯道转角正相关.

Calibrating of acceleration and deceleration rate for the operating speed prediction models of two-lane roads in a mountainous area

To determine the acceleration and deceleration rate for the operating speed prediction model, the continuously driving tests of passenger car, bus, and heavy trucks were carried out on two-lane roads in a mountainous area. Longitudinal acceleration of vehicles was collected, and the cumulative frequency curves of peak acceleration and deceleration rate were analyzed. The statistical distribution and the eigenvalues of acceleration (a_x) and deceleration (a_b) were obtained, and the models of a_x and a_b with road geometry parameters as independent variables were established. The results show that: due to that the magnitude of a_b of passenger cars is about twice higher than a_x, the a_x and a_b could not be simplified to a same fixed value. Slope breakpoint of cumulative frequency curve of a_x and a_b does not appears on the 85^th percentile but near the 95^th percentile. The a_x and a_b of large buses display very close amplitude, and a_b of heavy-duty trucks is significantly greater than a_x. a_x and a_b of heavy-duty trucks are lower than large buses''. There is a negative correlation between longitudinal acceleration of passenger car and curve radius, and a positive correlation with curve deflection angle.