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Improved Surface Drainage of Pavements

The purpose of this project was to identify techniques for improving the drainage of multi-lane highway pavements and to develop guidelines for implementing the most promising of these techniques. The drainage of highway pavement surfaces is important in the mitigation of splash and spray and hydroplaning. This study focused on improving surface drainage to reduce the tendency for hydroplaning. The main factor affecting the propensity for hydroplaning is the thickness of the water film on the pavement surface. Three general techniques were identified for reducing the water film thickness: controlling the pavement geometry, the use of textured surfaces to include porous asphalt surfaces and grooved surfaces, and the more effective use of drainage appurtenances. The prediction of the water film thickness is based on the use of the kinematic wave equation as a model to predict the depth of flow on pavement surfaces. Data supporting the model were obtained from the literature and from studies conducted to measure Manning's n for a brushed concrete surface and for porous asphalt surfaces. Expressions for Manning's n as a function of Reynold's number were developed for portland cement concrete, concrete, asphalt concrete, and porous asphalt surfaces. Full-scale skid testing was also conducted on grooved and brushed concrete surfaces and on porous asphalt surfaces; texture measurements were obtained for all of the tested surfaces (laboratory and field). The results have been integrated into an interactive computer program, PAVDRN. This interactive program allows the pavement design engineer to select values for the critical design parameters. The program then predicts the water film thickness along the line of maximum flow and determines the hydroplaning potential along the flow path. If the predicted hydroplaning speed is less than the design speed, the designer is prompted to choose from alternative designs that reduce the thickness of the water film.