Abstract: It is easy to have water at super-elevation section of S curve in rain，which affects the traffic safety． According to the difference of super-elevation gradient direction，the gradient sections are divided into the same change direction and the opposite of cross slope． The calculation models for flow path length of super-elevation section are established by dynamics and FDM． Considering the vehicle in hydroplaning danger state，the control length of flow path is obtained． Taking S curve of highway arch as the research object，flow path length of transition section whose super-elevation value is from -2% to 2% is analyzed，with 3 different types of lane numbers and 7 different types of longitudinal slopes． The results show that when longitudinal slope is increased from 0． 5% to 6% ，the average flow path length increases 2． 83 times; the larger longitudinal slope，the longer of flow path length; when longitudinal slope is greater than 4% ，the prescribed values of different lanes all exceed． Taking the flow path length as the control index，the proposed maximum longitudinal slope values at super-elevation section of S curve with different lanes are put forward．

Key words: S curve, super-elevation, transition curve, longitudinal slope, flow path length

摘要： 雨天公路 S 型曲线超高缓和路段易形成积水，影响行车安全。以力学为基础，运用有限差分，建立了超高渐变段的水流路径长度与纵坡的关系模型; 考虑车辆发生滑水的危险状态，得到水流路径控制长度。以公路单路拱 S 型曲线为研究对象，对 3 组不同车道数和 7 种不同纵坡工况下的 ±2%超高渐变段的水流路径长度进行分析。结果表明: 纵坡由 0． 5%增加到 6%，水流路径长度平均增大 2． 83 倍，纵坡越大，水流路径越长; 当纵坡大于 4% 时，不同车道的水流路径都超过了限定值。以水流路径长度为控制指标，给出了不同车道数 S 型曲线平缓超高路段最大纵坡建议值。

关键词: S 型曲线, 超高, 缓和曲线, 纵坡, 水流路径长度