Studies of pavement skid resistance in Kentucky have been in progress since 1956. In 1964, an extensive investigation into the use of an automobile as a testing tool was undertaken and an interim standard method of test was selected. Since then, investigations with the device have continued, both to facilitate meaningful interpretation of skid-test data and to evaluate the skid resistance performance of pavement surfaces.

Variables associated with the testing device, procedures and pavement surfaces were investigated. Several paving projects were tested to determine the number of sites required to obtain a representative result. It was found that on most surfaces, the coefficient of friction varied relatively little, but that testing of two sites was desirable to insure a representative measurement. Tests with two different sets of ASTM E-17 standard test tires having nearly equal service life yielded identical results. Limited investigations on the effect of seasonal and temperature changes on skid resistance were conducted.

The polishing of pavements due to traffic, time in service, and year-to-year climatic differences were considered in order to ascertain the frictional characteristics of various pavements. Every type of pavement, sealing, and deslicking treatment used on Kentucky's state road system were monitored and assessed as to their frictional properties. The skid resistance of bituminous and portland cement concrete pavements were related to cumulative traffic. A regression analysis indicated that skid resistance on bituminous pavements decreased approximately 20 percent during the first million vehicle passes. The decrease was less rapid thereafter, being about 8 percent during the second million and about 6 percent during the !bird. A decrease in the coefficient of friction on portland cement concrete pavements due to traffic polishing was evident, but was less than on bituminous pavements. Kentucky rock asphalt surfaces retained high skid resistance regardless of in-service life or traffic exposure. Data on sand asphalt surfaces were not sufficiently complete to generalize about its skid resistance characteristics; however, several of the pavements did exhibit rather low coefficients of friction for the traffic sustained. For this reason, five experimental sand asphalt surfaces were constructed in 1968. Initial measurements on these surfaces are presented.

Report Date


Report Number

No. 292

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The opinions, findings, and conclusions in this report are not necessarily those of the Department of Highways or the Bureau of Public Roads.