Abstract: In order to determine the safe speed of a passenger car on bends in rainy environments, a sideslip speed model considering longitudinal slope, braking acceleration and tire load transfer was established based on the instantaneous axis. The friction coefficients under different water film thickness were collected on the spot, and the regression equation between them was obtained. Combined with the principle of friction ellipse, a comprehensive friction coefficient distribution method considering braking and driver behavior characteristics was obtained. The calculation flow chart for determining the speed on bends was proposed, and the vehicle speed on bends with lateral sideslip and longitudinal parking as indicators under different rainfall intensities was obtained. The research results show that when the water film thickness is 0, the obtained sideslip velocity value is about 35% lower than that of the point mass model. When the water film thickness is less than 2 mm, the friction coefficient decreases fastest and has the greatest influence on the vehicle speed. When the water film thickness is greater than 2 mm, the friction coefficient changes little, and its law is not obvious. Rainfall has a significant impact on the safe speed of passenger cars on curves, and the average speed is reduced by about 15 % when only light rain occurs. When the general minimum radius is used to calculate, the longitudinal parking speed is all smaller than the lateral sideslip speed under different rainfall intensities.

Key words: traffic engineering; rainfall environment; friction coefficient; vehicle sideslip; curve speed

摘要： 为了确定降雨环境下小客车弯道安全车速，基于瞬时轴线，建立了考虑纵坡、制动加速度及轮胎荷载转移的小客车侧滑速度模型；通过实地采集不同水膜厚度下的摩擦系数，得到了这二者之间的回归方程；结合摩擦椭圆原理，得到了考虑制动、驾驶人行为特性的综合摩擦系数分配方法；提出确定弯道车速的计算流程图，得到了不同降雨强度下以横向侧滑和纵向停车为指标的弯道车速。研究结果表明：当水膜厚度为0时，得到的侧滑速度值比点质量模型低35%左右；当水膜厚度小于2 mm时，摩擦系数降低最快，对车速影响最大；当水膜厚度大于2 mm时，摩擦系数变化幅度小且规律不明显；降雨对小客车弯道安全车速影响显著，仅小雨时就会导致车速平均降低15%左右；取一般最小半径计算时，不同降雨强度下的纵向停车速度均小于横向侧滑速度。

关键词: 交通工程；降雨环境；摩擦系数；车辆侧滑；弯道车速