November 2007
Publication No. FHWA-HRT-08-026

Foreword

Signs are considered essential to communicating regulatory, warning, and guidance information. It is critical that signs are able to fulfill this role during both daytime and nighttime periods. The ability of a sign to fulfill its role during nighttime periods is provided by a unique form of reflection known as "retroreflectivity." The retroreflectivity of signs, however, degrades as the signs age in the field. A new standard in the Manual on Uniform Traffic Control Devices (MUTCD) requires that agencies maintain traffic signs to a minimum level of retroreflectivity. Various methods can be used within an agency's sign management processes to meet and maintain a minimum retroreflectivity requirement for traffic signs. This report describes methods for maintaining traffic sign retroreflectivity that can be used by agencies to:

• Systematically identify those signs that do not meet the minimum level of retroreflectivity.
• Initiate activities that will upgrade signs that fall below the minimum required levels.
• Monitor the retroreflectivity of in-place signs.
• Create procedures that will assess the need to change practices and policies to enhance the nighttime visibility of signs.

It is not appropriate to prescribe a single detailed method for all agencies to follow. The most cost effective and efficient method to maintain sign retroreflectivity will vary by agency, depending on the types of signs in service and the traffic and environmental conditions. Therefore, this report outlines several possible methods an agency can employ to maintain a minimum level of traffic sign retroreflectivity.

Michael F. Trentacoste
Director, Office of Safety
Research and Development

Notice

This document is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for the use of the information contained in this document. This document does not constitute a standard, specification, or regulation.

The U.S. Government does not endorse products or manufacturers. Trademarks or manufacturers' names appear in this report only because they are considered essential to the objective of the document.

Quality Assurance Statement

The Federal Highway Administration (FHWA) provides high-quality information to serve Government, industry, and the public in a manner that promotes public understanding. Standards and policies are used to ensure and maximize the quality, objectivity, utility, and integrity of its information. FHWA periodically reviews quality issues and adjusts its programs and processes to ensure continuous quality improvement.

Form DOT F 1700.7 (8-72)

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized

SI* (MODERN METRIC) CONVERSION FACTORS

*SI is the symbol for the International System of Units. Appropriate rounding should be made to comply with Section 4 of ASTM E380. (Revised March 2003)