Monitoring Pavement Surface Macrotexture and Friction

Abstract

The amount of available friction and texture depth are primary concerns in the evaluation of pavement surface safety characteristics. The two components of microtexture and macrotexture provide pavement surface friction. Macrotexture properties are collected with laser-based devices at highway speeds, but a proper evaluation of microtexture is available only with stationary devices or laboratory experimental methods. The industry is trying to develop practical methods for monitoring microtexture at the network level. Pertinent quantification for both friction components is valued because the common locked-wheel testing of skid resistance depends on surface temperature, presence of dirt and oil on the road surface, and vehicle speed. This case study examined the relationship between laser-based mean profile depth (MPD) and the friction number (FN) collected with a locked-wheel skid trailer on Louisiana highways. The analysis showed that quantified microtexture data were required in conjunction with the macrotexture to establish a significant correlation with friction measurements. However, the correlation between MPD and FN appeared to be significantly stronger at higher speeds of friction testing. Lower and higher threshold values were determined from the first and third quartiles of MPD and FN data. At speeds of about 50 mph, 71% of the pavement sections with MPD of less than the lower texture threshold also had FN values of less than the lower friction threshold. This lower MPD threshold of 0.036 in. can be implemented in network-level monitoring operations to determine areas of concern that require friction testing.