Correlation of pavement surface texture to hydraulic roughness

A study was performed to determine whether a correlation exists between the pavement's texture parameters, as determined by the outflow meter, texture beam, sand patch, and texture van, and the hydraulic roughness of the same pavement as measured by Manning's n-value. Because of an ever-changing texture from weathering and traffic, it is not practical to test for hydraulic roughness in the field. Therefore, the project incorporated the use of a laboratory hydraulic flume to perform flow tests on 10 different pavement types found in the field. Because wet pavements are a cause of many highway accidents as a result of hydroplaning, a correlation between surface texture and hydraulic roughness will help an engineer to determine whether a hydroplaning problem exists for a given rainfall intensity. From testing it was found that relationships exist between the texture and hydraulic roughness. It was also found that the outflow meter results were inversely related to pavement texture. With this information the engineer can use a simple texture-measuring technique to estimate the hydraulic roughness coefficient.