Field Evaluations of Warning and Regulatory Signs with Enhanced Conspicuity Properties

Abstract

Researchers examined the impacts of various sign conspicuity enhancements on traffic operations and driver behavior in Texas. Eight types of applications were evaluated: fluorescent yellow chevrons, fluorescent yellow chevron posts, fluorescent yellow curve signs, fluorescent yellow ramp advisory speed signs, fluorescent yellow stop ahead signs, fluorescent red stop signs, flashing red light-emitting diode (LED) stop signs, and a standard red border on speed limit signs. Fourteen sites were used for the evaluations. Traffic operations data collected before and after the sign upgrades included vehicle speeds, edge line encroachments, and stopping compliance. Many statistically significant beneficial results occurred, including the following: fluorescent yellow chevron signs produced a significant reduction in curve speeds and edge line encroachments, both the fluorescent red and LED stop sign treatments reduced the number of vehicles not fully stopping, and the standard red reflectorized border on the speed limit sign produced a significant improvement in speed limit compliance. The data showed no undesirable impacts for the measures of effectiveness for any of the signing treatments. On the basis of the findings, the researchers recommend fluorescent yellow chevrons for full implementation. The other fluorescent yellow signs evaluated in the research are recommended for implementation on an as-needed basis. Microprismatic stop signs and flashing LED stop signs are also recommended for implementation on an as-needed basis. Although found to be effective, the red border speed limit sign currently should be limited to experimental implementation, as permission is required from FHWA to install these signs. The fluorescent red stop sign is not commercially available at this time.