• Existing pavement structure/history (including past preservation treatment applications). • Traffic loadings. • Distress types (e.g., faulting, cracking, spalling), severity levels, and amounts. • Overall condition indexes/ratings. • Surface profile/smoothness. • Surface friction and macrotexture. • Nondestructive testing (NDT) data (e.g., deflections, load transfer efficiencies, and back-calculated layer moduli). In the pavement preservation realm, pavement management data are very important in determining (1) whether a project is a suitable candidate for preservation, (2) which treatments are feasible for a project, and (3) which treatment is most ideal in terms of cost effectiveness and other considerations. Performance indicators, such as overall condition indexes/ratings, smoothness indexes, and key distress measures, can be used to establish the pavement preservation window that defines when preservation should be considered for a project. Likewise, these same performance indicators can be used to set trigger and threshold levels for individual treatments that govern when they should be considered. Historical condition and performance data can be used to develop time-series pavement performance models, which can be used to select the preferred project treatment based on expected performance and cost effectiveness. A survey by the FHWA Pavement Preservation ETG Rigid Subcommittee examined highway agency practices regarding how concrete pavement preservation is integrated into the pavement management systems of state highway agencies (Scofield et al. 2011). Of the 38 responding highway agencies, 23 indicated using trigger values for concrete pavement management/preservation. Among these agencies, smoothness is one of the commonly used indicators for trigger and/or threshold criteria for preservation treatments, although overall condition and key distresses (such as joint faulting and slab cracking) are sometimes used. Nine highway agencies (Kansas, Michigan, Minnesota, New Jersey, North Carolina, Oklahoma, Pennsylvania, South Carolina, and Washington) were identified as having best practices for use of trigger values. As examples, Tables 2.3 and 2.4 highlight the criteria used by Michigan and New Jersey Departments of Transportation (DOTs), respectively. It is noteworthy that the state practices survey showed very little use of friction and other individual distresses (besides faulting and cracking) for decision criteria for applying preservation treatments. Because preservation objectives and functions are somewhat broad, there is Table 2.3. Michigan DOT Criteria for Preservation Strategies (Scofield et al. 2011) Minimum RSL DI RQI IRI 7 < 20 < 54 < 107 Joint Resealing 10 < 15 < 54 < 107 Crack Sealing 10 < 15 < 54 < 107 Diamond Grinding 12 < 10 < 54 < 107 Dowel Bar Retrofit 10 < 15 < 54 < 107 Concrete Pavement Restoration* 3 < 40 < 80 < 212 Strategy FDR *Consists of full-depth concrete repairs, diamond grinding, and other. RSL: Remaining service life DI: Distress index RQI: Ride quality index IRI: International roughness index Table 2.4. New Jersey DOT Criteria for Preservation Strategies (Scofield et al. 2011) Condition Status Condition Index Criteria Engineering Significance Poor IRI > 170 or SDI < 2.4 Roads overdue for treatment Fair 95 < IRI < 170 and SDI > 2.4 or IRI < 95 and 2.4 < SDI < 3.5 Roads exhibit minimally acceptable ride Good IRI < 95 and SDI > 3.5 Roads exhibit good ride quality IRI: International roughness index SDI: Surface distress index Chapter 2. Preventive Maintenance and Pavement Preservation Concepts 13 Ch 2. Maintenance and Preservation The availability of the above information is an essential part of the process of managing a successful preservation program. Successful programs exploit the data available from a pavement management system (PMS) to help in the decision-making process. Although highway agencies collect and analyze pavement management data in different ways, the importance of using the following types of data to assess needs and to program and apply a range of treatments is widely recognized: