Abstract
The human factors study being reported measured drivers’ estimates of horizontal curvature as a function of the size and spacing characteristics of post-mounted delineators. The study also assessed drivers’ understanding of delineator color applications. The main objective of this study was to provide support for simplifying delineator applications of FHWA's Manual on Uniform Traffic Control Devices for Streets and Highways (MUTCD), particularly the need to distinguish between single and double delineators and the need to have variable approach and departure horizontal curve delineator spacing. A closed-course nighttime study was conducted with 24 drivers aged 22 to 72 in a passenger sedan with low-beam headlights. Drivers rated their estimates of curvature for large- and small-radii curves from three stationary viewing distances. In addition, participants completed a test of their memory for the proper placement of yellow and white reflectors using photographs of roadways. Results from the visibility study show that drivers cannot distinguish between single and double delineators and they cannot distinguish between variable spacing and fixed spacing on approaches to horizontal curves. The results from the photograph test show that drivers do not understand the difference in placement for yellow and white delineators. As a result, the recommendations include the elimination of the single versus double delineator distinction in MUTCD and the use of a fixed spacing pattern for delineators on the approach to and departure from horizontal curves.
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