AN IMPLEMENTATION GUIDE FOR MINIMUM RETROREFLECTIVITY REQUIREMENTS FOR TRAFFIC SIGNS

Although the Manual on Uniform Traffic Control Devices (MUTCD) stipulates that all warning and regulatory signs be illuminated or reflectorized to show the same color and shape by day or night, there are no specific guidelines for required retroreflectivity levels. Therefore, the Federal Highway Administration (FHWA) embarked on a comprehensive research program which resulted in recommended guidelines for minimum retroreflectivity values for four types of signs: yellow or orange warning signs, white on red regulatory signs, white regulatory signs, and white on green guide signs. The retroreflectivity values developed for each group of signs are considered the retroreflectivity levels below which the sign would be inadequate for meeting the nighttime visibility requirements for most drivers, and therefore, should be programmed for replacement. To assist agencies in developing a cost-effective program for timely replacement of ineffective signs, this document was prepared. Initially the report describes the principles of retroreflectivity, the types of retroreflective materials, and the proposed minimum retroreflectivity guidelines. Then, the report presents the concept of a sign management system, and provides guidance for developing a sign inventory, conducting sign inspections, and maintaining signs. The report concludes with discussing options that State and local agencies can follow for replacing their ineffective signs and offers a minimum and desirable program.