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Chapter 2. ANALYSIS DEVELOPMENT This chapter describes the development of the analysis methods used for computing the impacts of heavy vehicles on local roads. While no new pavement design or analysis methods were developed as part of this project, some existing methods were utilized in different ways to accomplish the analyses required. In order to estimate the impacts of heavy vehicles on local roads, the basic analysis was developed to compare two traffic conditions — with and without the heavy vehicles in question. The tool that was developed incorporates this overall method and implements it in two modes of analysis — at the level of the individual road segment and at the network level. Analysis Modes For an individual road segment analysis mode, more detail may be included in the analysis, including specific numbers and types of heavy vehicles, and the user is able to modify the default pavement structure data if new information is available. Other things that the user is able to modify at the segment level include the traffic (average daily traffic, heavy commercial average daily traffic, etc.) and the condition of the roadway segment over the past three pavement condition surveys. The network mode conducts the heavy vehicles effects analysis in the same way as for the segment mode, but does not allow the user the flexibility to modify individual components of the inputs such as those described in the previous paragraph. In this mode, the tool takes the data that had been previously imported from a pavement management system (PMS) for the roadway network and uses them in the analysis. In the network mode, the user is still able to specify the number of heavy vehicles and their characteristics. The network mode may take several minutes to conduct its analysis, depending on the size of the network and the speed of the computer. The next sections in this chapter describe the general analysis methods utilized by the tool, and interpretation of the results that it generates. General Analysis Components This section describes the basic analysis conducted by the heavy vehicles impacts tool, including the following steps. • Collect and validate data • Compute ESALs (with and without specified heavy vehicles) • Analyze existing pavement structure • Estimate additional bituminous material required for the specified heavy vehicles • Estimate additional pavement life consumed due to the specified heavy vehicles • Estimate degradation in pavement performance curves with and without heavy vehicles • Compute quantities and costs • Report results 14