In an effort to develop guidelines for highway geometrics and pavement surface characteristics which will ensure adequate vehicle control during anticipated maneuvers on highway sections containing a combination of horizontal curvature and vertical grade, an extensive analysis was performed of accident data, computer simulation studies were made, and an in-depth investigation was made of two high-accident sites. The results of the study indicate that drivers are not likely to loose control of their vehicles on curve-grade sites unless they are attempting to perform severe maneuvers on slippery road surfaces with fair to poor tires. It is noted that the AASHTO design procedures as described in "A Policy of Geometric Design of Rual Highways, 1965" and a "Policy on Design of Urban Highways and Arterial Streets, 1973", provide sufficient guidance for geometric design of sites with combined horizontal curvature and vertical grade, provided (1) the selected values of superelevation are large enough to result in adequate pavement surface drainage, and (2) the pavement skid resistance is sufficient for anticipated vehicle maneuvering. Due to the safety implications of the findings and the fact that they are based on both computer simulation studies and accident analysis, certain actions are suggested. AASHTO procedures are briefly reviewed and comments are made on highway agency superelevation practices, reducing driver demand, and existing high-accident sites.

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Filing Info

  • Accession Number: 00097151
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Sep 10 1975 12:00AM