Traffic signs are very important components of streets and highways. Ideally, they help motorists find their way in a safe manner by providing for the orderly and predictable movement of traffic. For signs to accomplish their intended purposes, they must be visible to the motorists. Although sign visibility is generally not a problem during daylight, signs with inadequate retroreflectivity may not be sufficiently visible at night and can contribute to accidents. In the context of this research, retroreflectivity is intended to encompass the characteristics of legibility, visibility, and conspicuity.
The objective of this project was to determine the economic consequences of alternative standards for retroreflective traffic signs. Accomplishment of the objective involved collection of retroreflectivity data on representative traffic signs in diverse geographic regions. Study areas included both urban and rural roadways and were large enough to adequately represent a range of maintenance conditions and classes of roadways. This study did not include construction and maintenance signs.
All work has been completed and the final report has been published as NCHRP Report 346, "Implementation Strategies for Sign Retroflectivity Standards." (See last page of this document for ordering information.)