Initial pavement smoothness has an effect on the future smoothness and life of asphalt concrete (AC) and portland cement concrete (PCC), as well as AC overlays of existing AC and PCC pavements. Initial pavement smoothness has a significant effect in 80 percent of new construction (both AC and PCC pavements) and in 70 percent of AC-overlay construction. Furthermore, using two different analysis techniques, added pavement life can be obtained by achieving higher levels of initial smoothness. Combined results of roughness-model and pavement-failure analyses indicate at least a 9 percent increase in life corresponding to a 25 percent increase in smoothness from target profile index (PI) values of 7 and 5 in./mi (0.11 and 0.08 m/km) for concrete and asphalt pavements, respectively.

The need to accurately characterize the structural condition of existing pavements has increased with the recent development, release, and ongoing implementation of the Mechanistic-Empirical Pavement Design Guide (MEPDG), developed under National Cooperative Highway Research Program Project No. 1-37A. A number of different material inputs are required in the procedure, and it is important that these be adequately characterized and defined so that competent structural designs can be developed. The analysis of deflection data collected with a falling weight deflectometer (FWD) provides a quick and reliable way of characterizing many of the parameters of the existing pavement layers. This paper summarizes how deflection data are incorporated into the MEPDG and describes two case studies, one with a flexible pavement and one with a rigid pavement. Significant findings and recommendations from the evaluated flexible pavement case study include the following: surface-down cracking is critical in the design of the hot mix asphalt (HMA) overlay, correction factors should be used for adjusting backcalculated layer moduli to laboratory determined values, and an FWD testing frequency of 30 Hz should be used for estimating the existing HMA modulus. For rigid pavements, the case study found that the thinnest overlay produced from the MEPDG was a bonded Portland cement concrete (PCC) overlay, whereas the HMA overlay was unreasonably thick. Within the design procedure, the manually entered k-value is used for unbonded and bonded jointed plain concrete pavements but does not appear to be used by the program in the HMA overlay design. The backcalculated dynamic (or static) elastic modulus should be used for the PCC layer, and the dynamic k-value should be used for the supporting layers. The backcalculated k-value representing the composite stiffness of all layers beneath the slab does not appear to have a significant influence on the design thickness for the pavement structure analyzed.

Materials-related distress (MRD) has affected many portland cement concrete pavements. Identifying the specific cause of MRD is not always possible, but with the use of appropriate techniques and a diagnostic approach, the cause can be determined in many cases. In a case studied as part of an FHWA project titled Detection, Analysis, and Treatment of Materials-Related Distress in Concrete Pavements, apparent MRDs were identified. In one case study, determination of the effective water-to-cement ratio (w/c) by epifluorescence microscopy was the key to understanding the cause of distress. The effective w/c, which may not be exact for a given concrete on an absolute basis, was used to compare two concrete microstructures on a relative basis. Stereo-optical microscopy, petrographic optical microscopy, and scanning electron microscopy were also used to identify the MRD diagnostic features present in the distressed concrete. As a result of this analysis, evidence of paste freeze–thaw and deicer attack was identified, but the principal cause of the distress probably was a high w/c in the distressed concrete.

The importance of surface texture characteristics to roadway safety was first recognized during the late 1940s and early 1950s when increases in traffic volumes and vehicle speeds resulted in increases in wet-weather crashes and fatalities. As a result, agencies conducted extensive research, including experimental projects around the country, to better understand and improve the surface conditions of portland cement concrete pavement in wet-weather conditions. As new surface-texturing methods were tried and evaluated, pavement engineers recognized that a general trade-off existed between friction and noise; that is, surface textures with higher friction tended to produce greater tire-pavement noise. Although considerable information exists on the influence of surface friction characteristics on safety and tire-pavement noise, it is dispersed among numerous sources. An effort is made to identify and summarize key texture-related information and recommendations based on the current state of the practice. Specifically, pavement texture nomenclature is introduced, methods of measuring and quantifying texture are discussed, traditional and innovative texturing methods and techniques are described, respective conclusions pertaining to the influence of texture characteristics on surface friction and tire-pavement noise are summarized, and current state-of-the-art texture-related recommendations are provided.

In recent years, FHWA has made a concerted effort to develop guidelines for the use of life-cycle cost analysis by transportation agencies and to promote the use of multiyear prioritization in pavement management. These efforts resulted in the development of a Technical Bulletin and Demonstration Project course materials that have been presented to state highway agencies throughout the country. A key part of multiyear prioritization is emphasis on the use of life-cycle cost information in cost-effectiveness calculations. An agency implementing multiyear prioritization as part of its pavement management system would naturally attempt to utilize the FHWA’s guidelines in developing the cost component of its economic analysis. However, because of the types of analyses required in pavement management and the ways in which cost information is reported and used, the recommendations provided in FHWA’s Technical Bulletin cannot be applied directly. The types of economic analyses that are used in an incremental benefit-cost analysis and the types of economic considerations that must be taken into account are discussed. Several of these economic considerations differ from the recommendations made in FHWA’s Technical Bulletin, so the reasons for these variations are also described.