Roadway traffic signs are a primary means of conveying critical information to roadway users. The Manual on Uniform Traffic Control Devices (MUTCD) provides the basic principles that govern the design and use of traffic control devices for all roadways open to public travel. In 1993, the U.S. Congress required that the Secretary of Transportation revise the MUTCD to include “a standard for a minimum level of retroreflectivity for pavement markings and signs which apply to all roads open to public travel.” It was meant to ensure that drivers, especially the elderly, be able to detect, comprehend, and react to traffic signs accordingly and help to facilitate safe, uniform, and efficient travel. To satisfy the congressional directive, FHWA added a table containing minimum sign retroreflectivity values (section 2A.08 of the 2009 MUTCD). In addition, several methods are identified that agencies can implement to maintain traffic signs at or above the minimum retroreflectivity requirements. The objective of this synthesis study was to provide examples of effective and advantageous practices that illustrate how different types of agencies can meet the retroreflectivity requirements. The aim of this study was to document the state of the practice and identify content that will assist other agencies that are exploring different methods for maintaining sign retroreflectivity. Information for this synthesis study was gathered from three distinct sources: published research, existing guidance and policy, and telephone surveys. (Author/publisher) This report is available online at http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_syn_431.pdf
Samenvatting