Abstract: Water film on road surface after rainfall induces a decrease of friction between tire and road.The risk of skidding increases as thickness of water film increases.To evaluate the influences of water film on vehicle safety,an inspection and evaluation method is thus proposed.The rainfall intensity in geometric design process of roads is generally determined based on the data from Hainan Province,China.The standard of thickness of after-rain water film is suggested considering the traffic safety.A case study is conducted on the highway designs,the thickness of water film corresponding to different geometric designs are inspected and evaluated.Optimization strategies are provided for unsatisfied road sections.The results indicate that the rainfall intensity at peak hours (50 mm/h) is suitable for evaluating drainage design of road pavements.The desirable limit of the thickness of water film is 2.5 mm,while the maximum thickness is 4 mm.The limit length of drainage path is 60 m.