David Randall Peterman
Analyst in Transportation Policy
Traffic signs provide information to help motorists travel safely. If a sign is useful during daytime, it has equal or greater value to motorists at night, when less of the road environment can be seen. Federal regulations have long required that traffic signs be visible at night, either through the use of retroreflective materials (materials that reflect light, such as from headlights, back in the direction from which it came) or through permanent lighting illuminating the sign. These regulations are part of the Manual of Uniform Traffic Control Devices (MUTCD), a compilation of federal regulations governing traffic control devices. Due to the costs and practical limitations on supplying electricity for lighting, agencies typically rely on retroreflective materials to make most traffic signs visible at night.
Retroreflective materials lose their reflective properties over time due to weathering and other factors. This reduces the visibility of the signs at night. To promote safety, the MUTCD also requires agencies to monitor their traffic control devices and make sure they comply with the federal requirements. Thus, agencies have been required to make sure that their traffic signs are visible at night, and to replace those which are no longer visible. However, for many years there was no objective standard establishing what level of retroreflectivity was needed for a traffic sign to be visible at night.
In 1992, Congress directed the federal Department of Transportation (DOT) to develop a standard for the minimum level of retroreflectivity that traffic signs (and pavement markings) must maintain. The Federal Highway Administration (FHWA) within DOT had already been doing research on the reflective properties of sign materials. Between 1993 and 2004 FHWA did further research and consulted with state and local transportation agencies regarding the implementation of the congressional directive. Between 2004 and 2007, FHWA completed a rulemaking to add a minimum standard for the retroreflectivity of traffic signs to the MUTCD. The new standard had three elements: it set a minimum measurable value for the retroreflectivity of traffic signs to ensure their visibility at night; it required state and local agencies to adopt a method by which to maintain the nighttime visibility of their traffic signs by 2012; and it required agencies to ensure that their signs were in compliance with the standard by 2018.
In 2009, the street sign lettering standard in the MUTCD was revised. This standard did not have a compliance deadline. In 2010, several press reports conflated the new nighttime visibility standard with the new street sign lettering standard. These articles made it appear that the federal government was requiring communities to replace traffic signs just to change their lettering style. Communities also complained about the cost of the new nighttime visibility maintenance standard (though the requirement that they replace traffic signs that were no longer visible at night was not new). Thus the nighttime visibility maintenance standard came to the attention of Congress.
In 2012, FHWA amended the compliance dates for the retroreflectivity standard (and several other MUTCD standards) to alleviate possible financial burdens the deadlines might have created for state and local highway agencies.
Date of Report: April 16, 2013
Number of Pages: 10
Order Number: R43042
Price: $29.95
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