Operational Effects of Drivers’ Misperception of Horizontal Curvature

Abstract

The effect of combining horizontal and vertical curves on operational conditions has been the subject of research over the last few years. A number of studies have reported that combining horizontal curves with crest and sag vertical curves would influence the curvature appearance of such combinations. According to these studies, drivers could misperceive the curvature of a horizontal curve when combined with a vertical curve, and this might result in negative operational effects. These negative effects would most notably be in the form of an erroneous driver’s speed choice. This study presents a driving simulation experiment that was planned and conducted to examine the effect of a driver’s misperception of horizontal curvature on the driver’s speed behavior. The simulation data were analyzed statistically and provided support for the hypothesis that drivers’ misperceptions of horizontal curvature affects their choice of speed. The effects of several geometric parameters on speed were also examined, including curve radius, algebraic difference of vertical grades, rate of vertical curvature, turning direction, superelevation rate, and sight distance.