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28 Measured Retroreflectivity It may be desirable to use the same or a similar system for multiple roadway items such as culverts, guardrails, road- Measurements should follow ASTM Standard E1709 way pavement, striping, no-passing zones, and sidewalks. with four or more readings per sign color. Agencies need to be committed to the long-term use The measured retroreflectivity method is best suited for and support of this method. The system is only valuable agencies with smaller sign populations. if the data are kept up-to-date and accurate. It is important that collecting readings be completed within a manageable timeframe. The measurement process need not consume excessive amounts of time that could result Blanket Replacement in other maintenance activities being neglected. Measurements are to be combined with other routine Replacement cycles need to be regular and staggered maintenance activities. For example, staff can collect evenly from year to year to help with planning, schedul- readings when examining sign supports or when repair- ing, and budgeting. ing knockdown signs. Agencies need to document blanket replacement details such as cycle length, procedures, and segmented road- ways/areas. Expected Sign Life Salvaging or reusing adequate signs could be consid- ered if resources are limited. Resources for service life values for sign sheeting materi- Records and work orders could be used to demonstrate als are available from FHWA, sign manufacturers, LTAP that signs are replaced within a reasonable and accept- centers, DOTs, nearby agencies, and research reports. able time period. Expected sign life systems can be used to extend sign service life, expedite maintenance operations, and help manage resources. Control Signs When selecting or developing a system, agencies should consider both existing and future needs and necessities. Temporarily borrowing or renting a retroreflectometer Systems should be able to expand and evolve over time. might be considered if purchasing a unit is not feasible. An agency must also be aware that systems may become Agencies should be able to justify their control signs' obsolete or experience technical difficulties. There needs sampling procedures. It is important to establish an to be contingency plans for salvaging important data or acceptable number of control signs and set appropriate transitioning to a new system. measurement intervals. It is best to gather a wide range of sign data in the initial It is important that measurement data be accumulated collection process to avoid having to collect additional and analyzed throughout the years to identify trends in information in a secondary effort. sheeting performance and sign deterioration. During the data collection process, it is beneficial to re- Control sign data could be used to establish regional examine signs on the roadway to identify where addi- service life periods for certain sheeting materials. The tional signs are needed, where changes need to be made regional data could then be used to extend service life to comply with the MUTCD, and where unnecessary for signs in the blanket replacement or expected sign signs could be removed. life methods.