Traffic Operational Impacts of Higher-Conspicuity Sign Materials

Researchers examined the impacts of various higher-conspicuity sign materials on traffic operations and driver behavior. A total of eight applications of microprismatic materials were evaluated: fluorescent yellow Chevrons, fluorescent yellow Chevron posts, fluorescent yellow Curve signs, fluorescent yellow Ramp Speed signs, fluorescent yellow Stop Ahead signs, fluorescent red Stop signs, flashing red light emitting diodes Stop signs, and a red border on Speed Limit signs. Researchers installed these signs at locations where it was believed that improving sign conspicuity would provide a statistically significant benefit to safety-related traffic operations. Traffic operations data collected before and after the sign upgrades included vehicle speeds, edge line encroachments, and stopping compliance. Overall, the higher-conspicuity applications produced mostly small changes in traffic operations, although many statistically significant beneficial results occurred. It should be pointed out that no negative driver behavioral impacts were found to be associated with any of the higher-conspicuity sign materials. Based on the findings, the researchers made recommendations pertaining to the application of higher-conspicuity sign materials. Fluorescent yellow Chevrons are recommended for statewide implementation. The other fluorescent yellow signs evaluated in the project are recommended for implementation on an as-needed basis. Microprismatic Stop signs are also recommended for implementation on an as-needed basis. Implementation of the flashing LED Stop sign and red border Speed Limit sign should be limited to an experimental basis, as permission is currently required from FHWA to install these signs. The fluorescent red Stop sign is not commercially available at this time.