Driver Response to Delineation Treatments on Horizontal Curves on Two-Lane Roads (0-5772-1)

The delineation of horizontal curves on two-lane rural roads is an important component of safety improvements to reduce run-off-road and head-on crashes. This project assessed four types of vertical delineation in conjunction with edgeline markings through a closed-course nighttime driving test, a survey of drivers using video clips of curves, and a field test of vehicle performance at four sites in rural Texas. The treatments evaluated were standard post-mounted delineators with a single reflector at top and one with retroreflective material the full length of the post, standard chevrons, and chevrons with yellow retroreflective material applied the full length of the post. The results show that vertical delineation of any type improves vehicle lane position at the entry and mid point of horizontal curves. Fully reflective postmounted delineators improved lane position and reduced encroachment more than standard posts. The two styles of chevrons performed equally well and both showed significant speed reduction when compared to pavement markings alone.