The purpose of the research reported was to develop tentative guidelines for highway geometrics and pavement surface characteristics to insure adequate vehicle control during maneuvers on highway sections containing a combination of horizontal and vertical alignment. The study tasks were to examine the factors that influence safe operations on highway sections having combined curvature and grade; determine those operating conditions that define the onset of skidding; evaluate by accident data analyis, simulation, and field studies the factors involved in skidding; and suggest measures for alleviating skidding accidents and recommend additions or modifications to current AASHTO design policies. Accident records from the Ohio and Pennsylvania Turnpikes were examined for influences of curvature and grade, Simulation and analytical studies of a wide variety of vehicle, curvature and grade, Simulation and analytical studies of a wide variety of vehicle, tire, road surface, geometric, and maneuver combinations were conducted to define and evaluate operating condition's leading to loss of control and the onset of skidding. Two sections of highway with high accident rates were selected and subjected to an indepth evaluation to determine accident causation factors. On the basis of the combined findings from an extensive analysis of accident data, computer simulation studies, and an indepth field investigation of two high-accident sites, it has been concluded that drivers are not likely to lose 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. (Author/publisher)
Abstract