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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 prin- ciples 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 âa standard for a minimum level of retroreflectivity for pavement markings and signs which apply to all roads open to public travel.â 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 congres- sional directive, FHWA added a table containing minimum sign retroreflectivity values (sec- tion 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 advanta- geous 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. The telephone surveys comprised the majority of the information in this report. The goal of the surveys was to identify what methods have been implemented and which have shown the most promise. The survey included 14 main questions and was designed to facilitate an open- ended conversation about sign retroreflectivity and general maintenance practices. Survey participants were public agencies with active programs for maintaining sign retroreflectivity. They were located and contacted through professional society e-mail lists, meeting announce- ments, professional contacts, agency websites, past presentation materials, and referrals; in some cases, it was the participants who expressed an interest and in other cases their par- ticipation was requested. Overall, 48 agencies participated, 40 that operate roadways open to the public that selected a method found in the MUTCD. The questions were e-mailed to the participants prior to scheduling a time for the interview, so that individuals had time to prepare their responses. During the telephone survey, the questions served as a guide for a general discussion about traffic sign issues and practices between the surveyor and the participant. Table 1 shows the distribution of the 40 agencies that have selected a method for replacing and maintaining a sign population. Within participant responses, it was determined that the expected sign life method was the most selected primary and secondary method for replacing and managing signs; the second most common was visual nighttime inspection; however, agen- cies were somewhat conflicted about this method. Survey participants were typically divided into two groups: agencies that have used nighttime inspection and agencies that rejected it. The primary reason for ending nighttime inspection was that agencies were concerned about staff- ing and did not want to add another activity to an already demanding maintenance schedule. The blanket replacement method was the third most selected method and agencies employing this approached generally praised it for its ease and straightforward application. Finally, a few agencies were implementing the measured retro reflectivity or control signs Summary PracticeS to manage traffic Sign retroreflectivity
2 methods. The cost for a retro reflectometer and time requirements for the measurements were the deciding factors. The survey responses identified several strategies and techniques that were labeled as effective practices. For the visual nighttime inspection, the most noteworthy practice was the implementation of training programs to ensure inspector proficiency. Resource man- agement tools were the most acclaimed benefit for the expected sign life method and it is important that agencies utilize sign information for planning, scheduling, and budgeting. Simplicity and ease were valued in the blanket replacement method; an effective practice to evenly and consistently blanket replace signs from year to year. A retroreflectometer can be expensive; however, its measurements can be very valuable, particularly in support of other methods. It is an effective practice to use the control signs method to justify the extension of sign warranty periods so that agencies can expand sign service life and maximize potential resources. Lastly, replacing signs based solely on retroreflectivity measurements can be time- consuming. If an agency has access to a retroreflectometer, it can be used in conjunction with routine daily maintenance; however, the readings should not detract from or eclipse other important activities. This synthesis also includes case studies of four agencies of various sizes that participated in the survey: the town of Clifton Park, New York; St. Louis County, Minnesota; the city of Phoenix, Arizona; and the Missouri Department of Transportation. Each case study dealt with different geographical and climatic conditions. Each case study provides detailed information about the agenciesâ sign replacement and management practices. These agencies have imple- mented effective combinations of methods and it was believed that providing additional detail to the readers was beneficial. Areas where survey participants thought there was a lack of guidance or information were also noted and compiled in this synthesis. Some of the areas suggested for further research included sheeting material color deterioration and the effects of nighttime inspection intervals on different sign populations. The need for monitoring the development of retroreflectivity measurement technology and creating a national database that would contain important infor- mation about the sign service life information of different sheeting materials from across the county is also discussed. This report concluded that survey participants were implementing a variety of primary and secondary methods for maintaining signs and ensuring retroreflectivity compliance. The expected sign life method was the most often selected followed by the visual nighttime inspec- tion and blanket replacement methods. Selection ranking aside, participant responses showed that each method exhibited distinctive advantages and operational benefits. Each of the meth- ods listed in the MUTCD were being used by at least one agency. Overall, each agencyâs approach for maintaining adequate signs was practical, versatile, and effective. MUTCD Assessment and Management Methods Primary Sign Replacement Method Secondary or Support Method Local Agencies* State DOTs Local Agencies State DOTs Nighttime Inspection 6 Measured Retroreflectivity 2 0 0 0 Expected Sign Life 11 4 11 Blanket Replacement 3 5 4 0 Control Signs 2 207 5 550 *Local agencies include towns, cities, counties, and one toll road agency. The sum of the Primary Sign Replacement Method columns numbers 40. The Secondary or Support Method columns add to a lesser number because there is no requirement that there be a secondary method and agencies may have multiple support methods. TAbLE 1 DISTRIbUTION OF METHOD SELECTION
