Traffic impact studies (TISs) are used by transportation agencies to forecast future system effects from proposed development projects, and to predict the useful life of a transportation project against a future expected land use scenario. The Oregon Department of Transportation (ODOT) Best Practices for Traffic Impact Studies project was completed because: (1) there is a perception that TISs are not as accurate as they could be; (2) there is variability in assumptions and inputs to predict traffic impacts; (3)impacts may not be accurately projected in TISs; and (4) the best decisions for the transportation system may not be made. The research model consisted of three steps: (1) analysis of case studies for actual developmentsto compare forecasted traffic conditions to actual post-development traffic conditions; (2) a literature search of the state of the practice by other jurisdictions; and (3) refinement assessment for topics of interest. Case study TISs were selected to compare forecasted traffic conditions to actual post-development traffic conditions by analyzing key variables used in traffic analyses. Results of these comparisons were mixed. Based on the case study results and additional research, a set of best practices wereidentified for key technical topics to consider in the scoping and preparation of TISs. The best practices supplement ODOT's development review guidelines, but are equally applicable to other transportation agencies and local jurisdictions.
Samenvatting