Post-construction evaluation of traffic forecast accuracy

This research evaluates the accuracy of demand forecasts using a sample of recently-completed projects in Minnesota and identifies the factors influencing the inaccuracy in forecasts. Based on recent research on forecast accuracy, the inaccuracy of traffic forecasts is estimated as the difference between forecast traffic and actual traffic, standardized by the actual traffic. The analysis indicates a general trend of underestimation in roadway traffic forecasts with factors such as roadway type, functional classification and direction playing an influencing role. Roadways with higher volumes and higher functional classifications such as freeways are underestimated compared to lower volume roadways and lower functional classifications. The comparison of demographic forecasts shows a trend of overestimation while the comparison of travel behavior characteristics indicates a lack of incorporation of fundamental shifts and societal changes.