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17 In the survey, two agencies were exploring the use of the ment, and necessity) of the sheeting, and predict the remain- measured retroreflectivity method as their primary approach ing life using expected sign life. for replacing signs. The first agency was a county with a population of approximately 114,000 residents in mostly Among the survey participants, 17 of 41 agencies uti- rural areas. The engineer estimated that there are approxi- lized this method as their primary means for replacing signs. mately 80,000 signs on 2,600 centerline-miles. The county Of the participants that selected alternative sign methods, attorney was concerned about tort liability and believed that 16 of the 24 agencies implemented some type assessment measured retroreflectivity would be the best method to ver- method system as a secondary method. Regardless of being ify sign compliance. The sign measurements would also be a primary or secondary method, there were many common recorded and tracked in a sign inventory system. The county aspects between both approaches. For this section, primary engineer would like to purchase several retroreflectometers and secondary methods that manage and track sign informa- for maintenance staff. The agency already inspects each sign tion were broadly referred to as an expected sign life system. and sign support once per year during daytime hours. The engineer envisioned that the maintenance staff would collect There were two basic ways that the expected sign life and record retroreflectivity measurements as they perform method was used. One way was to build an inventory, assess their yearly inspections. Signs would be replaced primarily the signs' condition (especially retroreflectivity), and then when the readings were near or below the minimum levels develop an estimate for the remaining number of years that to extend sign use. This participant reported that the method the signs could be in service. The second way to implement was still being developed. Overall, the county planned on the expected sign life method without building an inventory combining existing maintenance activities with an additional is to start installing date stickers on the signs. step to ensure sign compliance and maximize service life. Regardless, agencies still need to have an estimate of their The other agency using the measured retroreflectivity signs' service life. Some agencies used the manufacturer's method was a toll road organization that operates a prominent warranty periods as a default service life and replacement bridge, multiple transit facilities, and approximately six miles period. A manufacturer's warranty period guarantees that a of roadway. The participant estimated that they currently sign will retain 80% of the original retroreflectivity levels manage about 400 signs. The agency used Type III sheeting over a certain time period and does not represent a sign's ser- and wanted to maximize the service life of existing signs. A vice life. A sheeting material can last significantly longer than few years before, a student intern created a basic sign inven- the warranty period. One city used a replacement period of tory system in Excel; however, the sign information had not 7 years for Type I sheeting. Others reported that their service been kept up to date. The initial plan was to b orrow a retro life replacement periods were based on past experience and reflectometer from the local LTAP center for up to two weeks. field observations. A few participants conducted formal stud- A team of maintenance technicians would collect retroreflec- ies to justify the extension of the previous replacement period tivity readings for all signs. They would also have a chance to with the purpose of maximizing resources. A Midwestern update and verify information in the existing sign inventory DOT's formal study extended the replacement period from system. The measurements would help to prioritize immedi- 14 to 18 years for Type III signs and they hope to achieve ate sign replacements and the updated information would be 20 years of service life for signs on overhead sign panels (24). used when establishing an expected sign life system where Service life replacement periods varied substantially; how- future replacements are based on service life periods. ever, 10, 12, and 15 years were common. Some of the litera- ture relevant to sign life was included earlier in this report. Expected Sign Life Apart from service life, most survey respondents acknowl- Of all the sign retroreflectivity maintenance methods listed edged that they were able to identify sign age from the date in the MUTCD, the expected sign life method was found to stickers that were placed on the backs of signs. The stickers be used the most often. Several of the LTAP centers rec- by themselves had little effect on maintenance; however, it ommended that agencies strongly consider some type of was generally agreed that this was a good practice. expected sign life system to better manage resources and track sign data. When asked if they had any advice to provide Beyond the installation of date stickers, an agency needs to other agencies, the most common response from partici- some type of structured and systematic approach for manag- pants was "know how many signs you have on the roadway." ing information and replacing signs such as in a sign inventory Although this method is based on individual sign replace- system. One basic method would be maintaining a collection ments, the practical implementation is centered on effective of photographs that depict roadway signs and document the management and organization of sign data. With the pend- installation date. An additional step would be to maintain a ing compliance dates on sign retroreflectivity, it appears that formal written list of sign information; however, when deal- agencies finally have the justification to build a sign inven- ing with large quantities of constantly evolving sign data, it tory, assess the signs' condition (specifically retroreflectivity is better to have a more robust system. Sign inventories are but other characteristics as well, such as hardware, place- described further later in this report.