	Introduction

Since 2007, the Federal Highway Administration (FHWA) has amended certain national standards for traffic signs. Some agencies also confused the new nighttime visibility maintenance standard, which originally included deadlines by which agencies had to comply with the new standard, with the new sign-lettering standard, which did not have compliance deadlines. There Are Two New Traffic Sign Standards

In 2007, FHWA updated the Manual of Uniform Traffic Control Devices standard governing the maintenance of the nighttime visibility (retroreflectivity) of traffic signs (§2A.08). Retroreflectivity refers to the reflection of light back from an object. The 2007 amendment set a minimum level of retroreflectivity for signs and required state agencies to adopt a method to ensure that signs met that minimum. This standard did not have a deadline for compliance. Some press reports have given the impression that the federal government is requiring communities to immediately begin replacing all street signs just to comply with the new lettering style standard, but this is incorrect. However, there was no measurable standard for what constituted "adequate retroreflectivity." In 1985, the Center for Auto Safety petitioned FHWA to add a minimum nighttime visibility standard to the MUTCD. In 1992, Congress directed DOT to develop a minimum standard, with this provision in the FY1993 Department of Transportation (DOT) appropriations bill:
SEC. The Secretary of Transportation shall revise the Manual of Uniform Traffic Control Devices to include—
(a) a standard for a minimum level of retroreflectivity that must be maintained for pavement markings and signs, which shall apply to all roads open to public travel ...

		Purpose

The reflective properties of sign materials decrease over time, due to exposure to sunlight and other factors. As an earlier version of the MUTCD put it, if a sign is necessary in the daytime, it has equal or greater value to motorists at night. But ensuring that traffic signs are easily visible at night benefits not only older drivers, but all drivers. To provide flexibility to agencies, the standard listed several methods that can satisfy this requirement, including
visual nighttime inspection from a moving vehicle by a trained sign inspector; measurement of sign retroreflectivity using a retroreflectometer; replacement of signs based on their expected life above the minimum standard for retroreflectivity; replacement of all signs in an area, or of a given type, at specified intervals, based on the expected life above the minimum standard for retroreflectivity of the shortest-life material used on the signs in that area or of that type; replacement based on the performance of sample signs that are monitored for loss of retroreflectivity; or other methods that are developed based on engineering studies. FHWA's final retroreflectivity standard tried to satisfy both the congressional directive to set a minimum retroreflectivity standard, by including a table of minimum numerical standards in the MUTCD, and the preferences of the state and local transportation agencies, by saying that not every sign needed to meet the minimum standard so long as agencies had a management process in place to maintain the nighttime visibility of their signs. One was concern on the part of agencies about the cost of compliance. The other was that several press reports conflated the requirement for replacing signs that were no longer clearly visible at night with the entirely unrelated new standard requiring mixed-case lettering on street signs, which was added in the 2009 update of the MUTCD. Most MUTCD standards, such as the lettering standard, do not have compliance deadlines. DOT has observed that the MUTCD already required agencies to maintain the nighttime visibility of traffic signs. DOT said it changed the deadlines to reduce the costs and impacts of the compliance deadlines on state and local highway agencies.
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.