Using Michigan's two trailer testing units, coefficients of wet pavement friction were measured at selected and random sites throughout the Lower Peninsula from 1971-1975. A correlation study was conducted between the two testers at speeds of 20 and 40 mph. Coefficients of friction obtained from the tester correlation were also analyzed individually to determine repeatability (variance) within each unit. The investigation also included tests at speeds up to 77 mph, use of smooth test tires, and measurement of wet peak friction. Skid test locations included varied surface types and textures on both traveled and untraveled roadways, and skid testing was performed during all seasons. Specific findings include: stopping distances on wet highways for a vehicle with smooth tires average 50% greater and may be over 150% greater than a vehicle with tread tires; friction tests made with smooth tires provide a valuable tool for evaluating pavement textures; friction values for a given test speed may be reliably estimated from values measured at lower speeds; seasonal variations in wet coefficient of friction values are significant, averaging 0.11 and varying up to at least 0.31; in evaluating a wet skid area, consideration should be given to the fact that pavement friction can cause stopping distance to vary by a factor of 2.5 and changing speeds from 20 tp 70 mph, varied stopping distances by a factor of 25; even though our two skid testers yield different friction values for any surface, correlation between the two units is so good that very small error is involved in transforming test values to a common standard; repeatability of the testing units is very good; and, in correcting temperature effects on tire/pavement friction, factors used for coarse textured surfaces must be different than for smooth textured surfaces. /Author/

  • Supplemental Notes:
    • Conducted in cooperation with DOT, Federal Highway Administration.
  • Corporate Authors:

    Michigan Department of State Highways & Transport

    State Highways Building, 425 West Ottawa, P.O. Box 30050
    Lansing, MI  United States  48909
  • Authors:
    • Copple, F
    • Luce, P T
  • Publication Date: 1977-1

Media Info

  • Features: Figures; Tables;
  • Pagination: 48 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00165546
  • Record Type: Publication
  • Source Agency: National Technical Information Service
  • Report/Paper Numbers: FHWA-R-1038 Final Rpt., FCP 41H2364
  • Contract Numbers: HP&R
  • Created Date: Jan 30 1978 12:00AM