Using a Road Surface Analyzer to Explain Noise Characteristics of Portland Cement Concrete Pavement Surface Texture

Uniformly spaced, transverse-tined portland cement concrete (PCC) pavements have been in extensive use in the United States since the early 1970s. Recent research by the Wisconsin Department of Transportation (WisDOT) and FHWA has led to an interim guideline for randomization of the tining pattern, with spacings varying from 10 to 40 mm and 50 percent of the spacings at or below 25 mm. At least five states have experimented with this random pattern. A six-state research study, funded by WisDOT and FHWA, was completed in 2000 by Marquette University and the HNTB Corporation. This study investigated 57 different PCC pavement textures, including a wide range of transverse and longitudinal tining patterns. One goal was to explain noise differences within and between various textures as well as to document noise and texture differences. The laser-based road surface analyzer (ROSAN), developed cooperatively by the Turner Fairbanks Research Center and private industry, was utilized for surface textural measurements. Before the advent of laser-based texture measurement devices, large studies of this type would have relied on manual volumetric (sand patch) measurements to quantify surface textural differences, making virtually impossible the determination of reasons for differences in noise characteristics of various textures. The use of ROSAN is described, tools developed to analyze textural variations and noise characteristics of tined pavement surfaces are presented, and correlations between ROSAN outputs and other variables, including noise level and sand patch measurements, are provided. Examples of simple and more subtle causes of noise discrepancies on random transverse tined PCC pavements are presented by use of ROSAN outputs. A great variation in surface texture, including tine spacing, width, and depth, was found among different PCC pavement sections constructed to identical tining specifications. Significant variations were also noted within any given test section in all states. A low correlation between ROSAN estimated texture depth and noise was observed. A more significant correlation between depth and width of tining was observed with use of ROSAN outputs. Recommendations include the need for quality control of tine depth, the need for a wet pavement accident study to determine tining depth requirements, and the development of an improved measurement device for measuring longitudinally tined PCC pavements.