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Federal Highway Administration Research and Technology
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Publication Number: FHWA-HRT-07-042
Date: April 2007
Maintaining Traffic Sign Retroreflectivity: Impacts on State and Local Agencies
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The analysis described in this report provides an estimate for the national impact of the proposed rule for minimum maintained traffic sign retroreflectivity at approximately $37.5 million, which will be incurred over a period of several years. Using a 7-year implementation period for regulatory, warning, and post-mounted guide signs and a 10-year implementation period for street name and overhead guide signs, the annual impacts are estimated to be $4.5 million for years 1 through 7 and $2.1 million for years 8 through 10.
The single direct impact of the proposed rule is the increased cost to agencies of using sign face materials with higher retroreflective properties. While that difference is 100 to 133 percent of the present cost of sign face materials, it only represents a 3 to 7 percent increase in the total sign cost.
If agencies are allowed to bring their sign systems into compliance over multi-year implementation periods, as is proposed, there are many cost elements that were included in previous estimates that are not directly attributed to the proposed rule. Elimination of these cost elements results in a significant reduction in the impact of the proposed rule.
Improved retroreflective sheeting materials provide longer service life than some sheeting materials used in the past, which may result in agencies experiencing reduced sign maintenance costs over time.
Agencies that develop new or improved sign assessment and management programs may realize reduced service life costs as they fully utilize the service life of installed signs.
Existing nighttime visual inspection programs typically identify signs in need of replacement well before they reach a level of retroreflectivity that is below the proposed minimum maintained retroreflectivity levels. The minimum levels were based on research substantially conducted under dark rural conditions with no glare. The human observer will evaluate the sign in its actual surroundings, which are complex and usually different than those conditions under which the proposed minimum maintained retroreflectivity levels were developed.
Research has not yet been able to provide a quantitative estimate of the safety and operational benefits attributed to improved retroreflectivity of traffic signs. Due to the complexity of the driving environment, and a limited ability to understand how drivers acquire, process, and react to information, it is doubtful that the impact of any single traffic sign can be quantified. However, good signage for both day and night conditions is believed to promote improved safety and traffic flow.
Tort liability regarding sign visibility at night does not historically appear to have been a problem. While the proposed rule will give potential litigators "numbers" to use, improved assessment and management programs, if followed by the agency, usually provide an adequate defense.