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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.
