The importance of the driver's receiving precise visual cues from the road environment
cannot be overstated. If the visual cues are confusing or in any way cause the driver to
incorrectly assess the approaching road environment, the crash risk of the driver may
increase. Of particular concern are the perceptual problems induced by superimposing
horizontal and vertical curves. To investigate the effect of overlapping vertical alignment on
the perceived horizontal curvature, dynamic and static computer-generated three …

Phase I of a study established that perception of horizontal curvature depends on the
overlapping vertical alignment. A horizontal curve radius will be perceived incorrectly if the
curve overlaps with a crest or sag vertical curve. Phase II quantified the extent of such
erroneous perception. An experiment involving a three-dimensional static presentation was
carried out to determine the mean value of perceived horizontal curve radius for different
sets of alignment parameters. The results of the experiment were analyzed statistically to …