Tennessee has been continuously engaged in skid resistance and corrective action research since 1952. A new program was initiated in July 1970 as a specific effort of inventorying the present skid resistant level of the State's primary highway system. The skid resistance level is measured with the University's two-wheel skid trailers that essentially meet the requirements of ASTM designation E 274 using the standard ASTM E 249 tire. The skid tests are performed on wetted pavements at a constant speed of 40 mph. Tests are conducted at intervals of approximately one-half mile or less in the inner wheel path of both lanes of the pavement. To date, 66 counties of the 95 counties within the State have been surveyed. This amounts to about 48 percent of the total rural highway mileage. For each test section base data on roadway goemetry, pavement surface characteristics, pavement type and date of construction, and the length of the test section are recorded for future evaluation.
The results of the skid measurements are summarized in tabular form and presented graphically. The graphical form depicts the measured skid number or coefficient of friction as related to the log mile along the highway surface. This type presentation provides a continuous log of the changes in skid number throughout a particular pavement construction section. In some instances, it can be readily seen that the type of construction influences the skid resistance level. Also, variations within a construction section can be readily identified. The results of the inventory are reported systematically to the State Highway Department, and, where indicated, corrective measures are taken. The corrective action may be complete resurfacing with a hot plant mix or the application of a seal coat.
Although intensive field and laboratory research has been sponsored during the past 19 years by the Highway Department, this project of inventorying all primary highway surfaces affords a systematic opportunity of pinpointing surfaces of questionable skid resistance level for corrective action. It is anticipated that the inventory and corrective action program will result in maintaining a satisfactory level of skid resistance on the roadway throughout the State and hopefully will result in the reduction of accidents. The data collected relative to characterizing the pavement surface and roadway goemetry will be useful in improving pavement design and construction techniques.