COMPUTER EVALUATION OF PAVEMENT TEXTURE VOLUME I--SUMMARY REPORT

This report describes a research study involving computerized evaluation of pavement texture. The central objective of the evaluation was to identify relationships between the surface texture and the frictional characteristics of pavements and to identify instrumentation systems that have the capability of measuring texture parameters at highway speeds. The two instrumentation systems that were extensively evaluated for capability to predict pavement friction from texture measurements were the light depolarization detection system and the Schonfeld stereophotographic interpretation system. Neither system yielded measurements of pavement texture which correlated highly enough with the frictional properties of pavements to make them practical prediction tools. A third system based on a noncontact laser profiling instrument was also evaluated, but it was found to have inherent limitations concerning resolution capability and complexity required for field implementation. Strong correlations relating the percent normalized gradient (PNG) to sand patch texture depth and other profile texture descriptors were identified. These results are extremely powerful for quantifying the variations of skid number with speed based on a single texture descriptor and the skid number of the pavement at a given speed. A computer program was developed for implementing this result. /FHWA/