TRB’s National Cooperative Highway Research Program (NCHRP) Report 535: Predicting Air Quality Effects of Traffic-Flow Improvements: Final Report and User’s Guide provides a recommended methodology to predict the long- and short-term mobile source emission impacts of traffic-flow improvement projects. Guidance is provided to evaluate the magnitude, scale, and duration of such impacts for a variety of representative urbanized areas. The report evaluates varying strategic approaches used to develop methodologies for estimating the impacts of traffic-flow improvement projects on mobile source emissions, reviews advanced methodologies used by leading metropolitan planning agencies, and offers suggestions to improve conventional travel models.

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