Practices to manage traffic sign retroreflectivity

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. 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 announcements, 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 participation 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, agencies 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 staffing 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 retroreflectivity or control signs.