Abstract: Based on the vehicle dynamics theory, the CarSim simulation software was used to establish a vehicle-road model on the ramp in order to study friction coefficient of the ramp road surface. Two typical driving conditions such as normal driving and braking at different speeds were designed. Three safety indicators were selected to evaluate the driving status of vehicles such as braking distance d, lateral offset distance l, and peak adhesion coefficient μmax, and three comfort indicators were also selected, including lateral acceleration ay and yaw rate ω and the braking deceleration (i.e., longitudinal acceleration) ax. Moreover, the threshold values of each indicator were determined. The safety and comfort analysis were conducted on the driving data of vehicles obtained from the simulation test, and the relationship curve among peak adhesion coefficient μmax, speed V and slope i was obtained. Linear and nonlinear regression analysis methods were used to fit the friction coefficient of ramp μ0, and the fitting formula for the friction coefficient of the ramp road surface based on the binary factor V-i was obtained. The results show that the friction coefficient of the ramp road surface increases with the increase of vehicle speed, and the increment continues to increase, and decreases with the increase of ramp slope and the change amplitude is relatively stable. The fitting formula can accurately predict the friction coefficient of the ramp road surface.

Key words: highway engineering; ramp; evaluation indicators; skid resistance; regression analysis

摘要： 为了研究匝道路面的摩擦系数，基于车辆动力学理论，采用CarSim仿真软件，建立了匝道上的车-路模型；设计了不同速度下正常行驶及制动2种典型行驶工况，选取了评价车辆行驶状态的3个安全性指标——制动距离d、侧向偏移距离l、峰值附着系数μmax，及3个舒适性指标——侧向加速度ay、横摆角速度ω及制动减速度（即纵向加速度）ax，确定了各指标阈值；根据仿真模拟试验获得的车辆行驶数据进行安全性和舒适性分析，得到了峰值附着系数μmax与车速V、坡度i的关系曲线；采用线性和非线性回归分析法对匝道路面摩擦系数μ0进行拟合计算，得到了基于V-i二元因素的匝道路面摩擦系数拟合公式。结果表明：匝道路面摩擦系数随着车速的增大而增加且增幅不断加大，随着匝道坡度的增大而减小但变化幅度较为稳定；拟合公式可以较为准确地预测匝道路面摩擦系数。

关键词: 道路工程；匝道；评价指标；抗滑；回归分析