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24 areas. With the blanket replacement method, the engineer however, as yet they have not conducted any formal stud- was not overly concerned about premature sign replace- ies on sign longevity. From its experience, red STOP signs ment and no signs were reused. It was acknowledged that and yellowgreen fluorescent School Zone signs have a ten- being able to document sign compliance and follow a routine dency to fade in color at a faster rate than other types of signs. schedule were acceptable tradeoffs. Routine blanket replace- Previously, the city requested that sign crews monitor these ments were staggered, which allowed the engineer to bet- signs and replace any signs when the color appears to have ter plan budgets and work schedules. Overall, the county's faded. Legend peeling on Regulatory and Warning signs was consistent and diligent approach has enabled it to maintain another problem. To address these issues, the city switched a high level of sign quality, which will allow them to easily from using black vinyl to acrylic materials, which has reduced meet the MUTCD requirements. the peeling and legend shrinking issues. Because of the harsh climate engineers continuously need to monitor sign quality Another key to the county's approach was reducing the and make small adjustments to extend service life. number of unnecessary signs. When St. Louis County changed sign inventory systems in 2010, it checked the accuracy and Concerning vandalism, there were high rates of spray location of most of the roadway signs. During this period, the paint-damaged signs in certain areas of the city. Phoenix has engineer made it a priority to remove any unnecessary signs. responded to this problem by applying anti-graffiti film to all The county received guidance from the Minnesota DOT's signs. Maintenance staff can now wipe off or wash a sign to Traffic Sign Maintenance/Management Handbook (22), remove spray paint and not have to replace the entire sign. which reported that over-signing was a critical issue and a The engineers were concerned about maintaining adequate substantial drain on resources. The engineer stressed that retroreflectivity levels; however, they have expressed more signs should be installed when there was a clear need. Plans concern about other issues that affect sign appearance and included removing special Warning signs that were deemed message content such as color fading. unnecessary, such as Deer Crossing symbol signs or Watch for Children signs. The engineer reasoned that the reduction The engineers previously used the blanket replacement in unnecessary signs could help drivers to focus on more method as its primary means for replacing signs. Blanket critical driving tasks and allow the county to conserve valu- replacement cycles were based on the city's experience with able resources. sign deterioration, because some materials would fail ear- lier than the specified in warranty periods. Because of the high vandalism rates and attrition, many of the signs on a Phoenix, Arizona given roadway that were scheduled for blanket replacement would differ in age. Maintenance staff would try to salvage Background and reuse adequate signs if they were one or two years old. Phoenix is the capital of Arizona and the sixth largest city in the United States. It encompasses 500 square miles and Phoenix has acknowledged that it has been diligent in sign is comprised mostly of developed urban areas. The city's maintenance and management; however, there have been dif- nickname is the "Valley of the Sun" and it is well-deserved. ficulties with dealing with such a large urban area with a harsh High temperatures in the summer routinely reach 110F and climate. Despite proactive measures, many city signs would the annual possible sunshine rate is 85% (25, 26). Phoenix not meet the MUTCD minimum retroreflectivity require- experiences an average annual precipitation rate of 8 in. ments. It was agreed that the city needed to take additional and the average wind speed is 6 mph. At the time of this action if it was going to meet the 2015 and 2018 compliance report, the city maintained an estimated 800,000 signs and dates. At the time, the city did not have a functioning sign 5,500 centerline-miles. Maintenance responsibilities were inventory system, but it did have detailed records of blan- divided into six different regions and each region had its own ket replacements in each of the six regions. Engineers used sign crews who were responsible for daily maintenance and these records to prioritize sign replacements and complete a sign replacement. cost estimate. It was estimated that to bring street name signs alone up to compliance would cost $11.5 million. Sign Replacement Method The engineers used the detailed cost information to secure stimulus money to fund blanket replacement of STOP and In Phoenix, the two issues that continuously affected the sign YIELD signs throughout the city. Additionally, they received inventory were the harsh climate and urban vandalism. First, a grant from a large sheeting manufacturing company to the constant sun and the high temperatures can cause some inventory and collect sign data for 14 major roadways. The materials to deteriorate faster. Type III signs in some parts of initial inventory covered only approximately 250 centerline- the country may last from 10 to 15 years; however, Phoenix miles of the total 5,500; however, it allowed the city to bet- reported that its Type III signs remained adequate for only ter manage resources on the more heavily traveled roadways. 8 to 10 years. The city recently changed to Type IV sign Using the aforementioned grant, the engineers planned to sheeting and hopes to extend the service life past 10 years; utilize an expected life sign approach and replace individual