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C H A P T E R 1 Introduction Background and with low-volume and low-speed roadways, and in many Problem Statement agencies, there is significant resistance to placing such treat- ments on roads with traffic volumes higher than a rather low The practice of pavement preservation (i.e., preventive main- number (say, between 500 and 2,000 vehicles per day [vpd]) tenance [PM] and some forms of minor rehabilitation and because of liability concerns (e.g., cracked windshields, chipped corrective maintenance) is a growing trend among transporta- paint) and a perception of lower quality (ride, materials, tech- tion agencies around the United States. Where perhaps 20 years nique, and so on). Furthermore, the use of PM treatments in ago no agency could claim to formally practice pavement general has long been associated with lower-volume roads, preservation, in the past decade alone a number of state high- where funding for higher-quality and higher-cost treatments, way agencies (SHAs) have created or formalized such pro- especially overlays, simply has not been available. As such, the grams. This list includes, but is not limited to, Rhode Island, use of PM treatments on high-volume roads is not considered. Arizona, California, Nebraska, Missouri, North Carolina, There is also an implied liability problem associated with Louisiana, Minnesota, South Carolina, and Nevada. At the the failure of certain treatments on higher-volume roadways. same time, other agencies that might have been practicing When a treatment fails on a higher-volume roadway, by defini- preservation for a longer time (such as Texas and Washington tion more people are affected and more people complain. There State) have extended their programs to cover a greater propor- may also be a perception that high-traffic-volume roadways tion of their pavement network than ever before. In recent are more likely to fail due to load rather than develop the type years, still other agencies (such as Illinois and Hawaii) have of functional deficiencies that are best addressed by pavement begun creating formal preservation programs. preservation. The significance of this trend in SHAs and other public The potential benefit of preservation on higher-traffic- agencies can be seen in several ways. Some agencies--such volume roadways might not be as readily recognized or as as those in North Carolina, Louisiana, California, and well documented. Also, because these pavements are typically Minnesota--have created a departmental position of pave- designed and built to higher standards than lower-volume ment preservation engineer. Many agencies have developed, roadways, they may deteriorate in different ways, rendering or are developing, formal guidelines for preservation, such as typical PM treatments less effective. Nonetheless, the preser- Ohio, Nebraska, Illinois, and California. Furthermore, Texas, Louisiana, and California have established pavement pres- vation of high-traffic-volume roadways is as important as the ervation centers, where researchers and practitioners work preservation of lower-traffic-volume roadways, because many together to improve preservation practices. In addition to conditions, such as the following, hold true for both: such centers, regional partnerships have also been formed to facilitate the exchange of ideas and best practices regarding Agency resources are limited, and it makes sense to use pavement preservation. available funding, personnel, and equipment in managing Based on transportation agency practices in this area, the pavements wisely. In the long run, pavement preservation growing significance of preservation practices is indisputable. saves money. However, the practice of preservation on high-traffic-volume Preservation provides benefits to the traveling public, includ- roadways is not nearly as common as it is on lower-volume ing safer and smoother roads. roadways. There are several possible explanations for this. For Preservation can be done more rapidly than rehabilitation, example, treatments such as chip seals have long been associated with fewer adverse effects on the traveling public. 6