Calculation and control of flow path length in superelevation sections

For the sake of researching the drainage on superelevation section, according to the character of the superelevation gradient process, the calculation models of flow path length for superelevation gradient sections with the same change direction and the opposite are built by FDM and multiple linear regression method. Then, Considered traffic safety and unfavorable drainage combination state with the critical water film thickness, the formula of the flow path maximum control length is deduced based on flow continuity and momentum theory. The maximum length of flow path should not exceed 41 m for highway in 80 km/h. Finally, the calculation model is verified to be workable and reasonable by the engineering example, and flow path length can be reduced by setting appropriate longitudinal slope or superelevation to improve the road surface drainage condition