The experience of New Jersey with pavements, like that of many other states, goes back to the last century. Highways constructed early in this century are still in service. During these extensive service lives, several maintenance and rehabilitation activities were applied to keep the pavements in good condition. These activities ranged from patching to full reconstruction. Also, most of New Jersey pavements have been widened at least once. With all these factors, it is difficult to identify the limits of homogeneous sections that should receive the same rehabilitation treatment. In 1996, the New Jersey Department of Transportation started a limited network level falling weight deflectometer (FWD) program. This program has short- and long-term goals. The short-term goals include identifying the limits of homogeneous sections (sectionalization), assessing the pavement structural capacity, estimating the remaining service life, and determining the future rehabilitation needs. The long-term goal of the project is to use the FWD measurements for the ongoing development and refinement of the models used to predict remaining structural life for use in economic evaluation models. The procedure followed to achieve the short-term goals of the project and an outline of the findings of the project are summarized.

Environment is one of the essential factors that influence pavement material behavior and consequently its performance. The variation of climatic patterns from region to region, coupled with the variation of site-specific conditions across North America, makes it difficult to develop standard models to account for seasonal variation in material properties that apply for all regions. Consequently, the need to develop regional models becomes an essential requirement for most transportation departments. The enhanced integrated climatic model (EICM) was evaluated to determine its suitability in predicting subsurface temperature and moisture conditions within New Jersey sites. The validation of the model used environmental data collected through pavement instrumentation of a large-scale research study under the sponsorship of the New Jersey Department of Transportation. Site-specific data were input to the model, and the model output parameters were compared against field-measured values. The results of the validation for two of the instrumented sites are reported. Results of the study do not indicate a high correlation between field-measured values and EICM-predicted temperature and moisture profiles for the various pavement layers.

Drainage characteristics have a significant effect on pavement performance. Pavements with poor subsurface drainage properties prematurely exhibit distress and have higher life-cycle cost. Shorter service life and higher maintenance cost are some of the reasons for the higher lifecycle cost. It has been proved in the last 20 years that subsurface drainage increases the pavement service life and reduces its life-cycle cost. A case study demonstrates and quantifies the benefits of providing subsurface drainage through reduction of moisture in daylighted base layers of flexible pavements. The effect of higher base course moisture content on the pavement in situ structural capacity was assessed through the analysis of deflection tests performed with the falling weight deflectometer. In this analysis, a structural adequacy index was used to assess the pavement structural service life. This information was then fed into a life-cycle analysis module to determine the effect of the higher moisture content on the pavement life-cycle cost. An increase in base course moisture content from 16% to 45% resulted in the reduction of pavement service life from 13 to 7 years. For a 40-year period, this translates to a three-fold increase in life-cycle cost for a 250-ft-long pavement section. Reducing moisture retention through various means, thereby improving the subsurface drainage quality of flexible pavement systems, can achieve substantial long-term savings.

The falling weight deflectometer (FWD) is commonly used to perform project-and network-level structural evaluations. Some highway agencies perform network-level FWD testing as a part of their pavement management systems to assess in situ structural capacity, remaining service life, and current rehabilitation needs. Through prediction models, future condition and needs are also estimated. In contrast, project-level FWD testing is typically performed as part of the rehabilitation design process. Calibrated FWD equipment provides repeatable data for a pavement section (i.e., data obtained with the same unit, at the same location, and under similar conditions). However, different FWD devices manufactured by the same or different manufacturers do not necessarily provide similar deflection basins when they test the same section, even if they are calibrated. This paper summarizes the results of a study performed for the New Jersey Department of Transportation to assess the differences among the FWD devices available in New Jersey and to correlate the results obtained with the different devices. Two rounds of testing were performed on flexible and rigid pavement sections located in the FAA William J. Hughes Technical Center in Atlantic City. The first testing cycle was performed in November 2002, and the second was performed in May 2004. The analysis results indicate that significant differences in repeatability and reproducibility may exist between different FWD devices.

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