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16 and accelerometers to record the vertical movement of the FWD tests at three sites per mile can provide statistically reli- vehicle. The profile is used in a simulation model to compute able results (31). the IRI (ASTM E1926, Computing International Roughness Index from Longitudinal Profile Measurements). The IRI is a Deflection measuring devices that collect deflections at summary measurement of the profile elevation changes of a traffic speed appear to be more appropriate for network-level roadway that represent the accumulated vertical movement of use. For example, the Rolling Weight Deflectometer (34) and a "standard" vehicle traveling on the measuring profile (28). the Danish Traffic Speed Deflectometer (35) provide more Although the IRI is fast becoming the standard to directly spatial coverage by measuring deflection at short intervals measure ride quality, there is a lack of standardization among and averaging results over a longer length to reduce scatter. transportation agencies in collecting the data, as is discussed These technologies bring new opportunities for network-level in chapter three. pavement management; however, they also add additional issues in terms of data quality management. Accurate and repeatable measurements are still difficult to obtain and these Surface Friction Properties technologies are not widely available. Because these devices are not currently being used for production surveys at the Transportation agencies monitor pavement friction because state and provincial level, these issues are not included in it affects wet-pavement friction and wet-pavement crashes; this synthesis. inadequate friction often leads to higher rates of crashes (29). Thus, friction measurements are typically conducted as part of the state's Wet-Accident Reduction Programs on areas TIME-HISTORY DATA COLLECTION ISSUES with high numbers of crashes (30). The friction properties developed at the tire­pavement interface can be measured One of the major challenges of successfully implementing through contact testing, non-contact testing, or a combina- and maintaining a PMS is ensuring consistency with legacy tion of both. State DOTs typically collect friction using the data when new techniques and technologies are implemented. locked-wheel device, a contact method. Noncontact testing Compatibility of the pavement condition data collection over (e.g., using profilers) are starting to be used to determine the time is very important for supporting effective pavement man- pavement macrotexture. The macrotexture measurements are agement. Quality time-series of pavement condition data are used to determine the change of friction with speed; pavement needed to develop reliable deterioration models, measure the with high macrotexture presents less reduction of friction impact of maintenance and rehabilitation treatments, develop with speed and is less probable to contribute to hydroplaning. multi-year work plans, and optimize the allocation of resources. The International Friction Index (IFI) uses macrotexture Therefore, it is important that the new and legacy data are properties in conjunction with friction testing to normalize compatible or can be made compatible through an appro- measurement made by different types of equipment (ASTM priate conversion. This applies to the actual data attributes E1960-98, Standard Practice for Calculating Friction Index (e.g., type of crack and length) and to the location referencing. of a Pavement Surface). The index is composed of two num- The use of appropriate metadata (i.e., data about the data) can bers, the friction value at 60 km/h (F60) and the change of facilitate the transition. The issue of ensuring consistency over friction with speed (sp). time is particularly important at the onset of adopting auto- mated technologies. This typically creates significant chal- lenges in terms of ensuring that the criteria and metadata are Structural Evaluation properly referenced. The structural capacity of a pavement segment is typically obtained by using nondestructive techniques, such as Falling Pavement Condition Data Consistency Weight Deflectometer (FWD) and/or destructive testing (i.e., coring and testing of the extracted materials) (31). FWD The first concern with the adoption of a new data collection testing is done by dropping a weight on the pavement and technology or with the contracting of a service provider is the measuring the deflection response at different distances from verification that the pavement characteristics measured are at the point of load application. If the layer thicknesses are known, least as accurate as the existing data and with agency protocols this information can be used to calculate the pavement Struc- and requirements. Furthermore, it is also important that the tural Number and modulus of the different layers (31). These new data can be processed to provide pavement condition properties can then be used to determine the remaining pave- indicators that are consistent with the agency's historical data ment structural capacity and service life. to allow time-history analyses. For example, it is important that automated crack detection systems provide the same rat- Agencies that have started to collect structural capacity ings as the agency's visual method. Verification tests could data at the network level generally agree that collecting data be included in the quality management programs to verify with a lower sampling rate than the one required at the project this agreement. Several DOTs have used a pre-qualification level is cost-effective and provides useful information (32, 33). process, in which they ask potential service providers to con- Studies in Kansas and Indiana have shown that performing duct measurements on several control sections for which the