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18 Blanket Replacement be removed from the roadway and used as backups or in reserve. Based on the county's experience, signs would typi- Blanket replacement was the third most selected method by cally last between 10 and 15 years. The county resurfaces or survey participants. Seven agencies use this method as their reconstructs certain roadways each year and during that time primary means for sign replacement and two agencies use it all signs on the resurfaced roadways would be replaced. One as a secondary approach. Agencies that employed blanket advantage to this approach of combining roadway resurfac- replacement often described it as simple and easy to imple- ing and sign replacement was that the funding would come ment, although this method did have its detractors. from the construction budget as opposed to the mainte- nance budget. In certain cases, there may be more funding The most common concern was the potential waste of and flexibility when dealing with the construction budget. labor and materials that came from replacing adequate signs. To reduce waste, the county borrowed a retroreflectometer A research report in 2006 examined past NCDOT sign bud- from the state LTAP center and measured signs that they per- gets and determined that the agency replaced 4.7% of the ceived to be salvageable. The salvageable signs were stored sign population as a result of vandalism or damage (13). One at the maintenance office and used as backup or in reserve. of the DOT participants tracked and monitored sign activities For example, if a STOP sign was knocked down during the throughout the state and estimated that for any given year weekend, a maintenance technician would use one of the sal- 10% of all signs were knockdowns. Another agency tracked vaged signs as a quick and adequate replacement. the installation of 3,000 signs from 1995 and found that approximately one-third remained on the roadway 16 years One county selected the blanket replacement method after installation. These examples illustrate that many signs because sign replacement could be easily documented. The will not last to the end of the blanket replacement cycles and survey participant was concerned about liability and a pos- there will always be replacements resulting from routine sible increase in tort lawsuits. The county attorney believed attrition. Regardless, many survey participants have been that blanket replacement was the easiest method to document able to successfully address the waste issue. and defend in court. For this agency, waste and removing adequate signs from the roadway were not major issues. Its Agencies using the blanket replacement method curtailed approach was to divide the county into different regions and sign waste by setting certain sign tolerance periods and try- sign replacements were staggered for a 10-year cycle, which ing to reuse adequate signs. For example, one of the surveyed was based on the warranty period. When a region was sched- DOTs implemented a corridor blanket replacement method uled for replacement, all of the signs were removed regardless with a replacement cycle of 15 years. That DOT has gathered of installation age and nothing was salvaged. The county kept empirical data and collected regional sign measurements records of work orders and sign replacements to verify that all to determine that certain sheeting materials can last up to signs were under warranty and within compliance. The agency 15 years and sometimes longer. During corridor replace- acknowledged that signs could last longer than the warranty ments, it would salvage and not remove any sign in the road- periods; however, it was more important to the agency to way that was less than three years old. Most signs in that state reduce liability than try to extend sign service life. were replaced after 15 years; however, some could have a maximum installation age of 18 years. In this instance, the blanket replacement cycle and tolerance period were based Control Signs on the DOT's experience and a certain level of comfort. The control signs method was another approach that few agen- Another DOT implemented a different approach to reduc- cies considered and only two agencies selected it as a primary ing waste and salvaging adequate signs. This DOT set the means of replacing signs. One of the agencies was actively blanket replacement cycle for roadway corridors at the implementing the method and the other was in the preliminary 10-year warranty period. The participant acknowledged that phases of determining formal procedures. Many participants most signs would be adequate after the warranty period, but did not thoroughly investigate this method because it requires they did not have a formal study to verify that the replace- both a retroreflectometer for collecting measurements and a ment cycle could be systematically extended. In the absence system for managing sign data. This method may take time to of such a study, the DOT utilized the visual nighttime inspec- implement but it does have advantages. tion as a secondary method to extend sign longevity and to ensure retroreflectivity compliance. Basically, the DOT set The agency implementing the control sign method estab- the blanket replacement cycle at 10 years, but would not lished it in 2007 and maintains approximately 32,000 signs. replace any sign that had been installed for six years or less. The county owned a retroreflectometer and had setup a sign With the combined methods, the maximum installation of inventory system that was developed in-house to manage and a sign was 16 years, and the nighttime inspection helped to track individual signs. Each year, maintenance technicians extend the use of a sign in lieu of a formal study. measured the retroreflectivity of 150 of the oldest signs for each sign color. These signs are in the field and are unpro- On a smaller scale, a participant from a midsize county tected. The sign inventory system was utilized to determine salvaged signs during blanket replacement, which would the locations of the oldest signs on the roadway. The oldest