Relationships Between Skid Numbers, Paving Materials and Mix Design, and Accumulated Traffic

About the report:

The objectives of this study were to determine the periods of time over which materials used in pavement surfaces provide adequate skid resistance and to classify various aggregate sources on the basis of the skid resistance qualities of the materials they produce. The objectives were achieved by evaluating the relationship between skid numbers from the Department's skid resistance survey program and various traffic volume measurements. As expected, skid resistance was found to be related to traffic volumes. It appears that total accumulated traffic volume and accumulated truck traffic volume both relate well to the skid resistance potential of aggregates. The skid resistance potential as related to accumulated traffic volumes of aggregate from various sources varies, but in most cases it is good; i.e., it remains above an SN40 of 40 for accumulated truck volumes in excess of 3 million. Only limestone aggregates utilized in sprinkle mixes were rated poor (SN40 < 30 for accumulated truck traffic of 3 million) It is recommended that a continuing study be undertaken by the Materials Division to utilize survey skid data for aggregate sources as was done in this project. Rankings in this report should, of course, be utilized as initial information for the Materials Division program. It is further recommended that the use of aggregates be judged on the basis of the ranking for the source and in consideration of the SN40 needs outlined in the report. Since most aggregates are rated "good", very little restriction in aggregate use would occur. Also, it is felt that "poor" and marginally rated aggregates could be utilized in situations where high skid resistance is needed, provided projected accumulated truck traffic volumes for the life of the mix indicate that sufficiently high SN40 values would be maintained.

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