Forecasting Net Induced Travel Demand for Optional Trip Purpose by Trip Production Model with Accessibility

Predicting net induced demand can be helpful for better feasibility study before investigating transportation infrastructure. The net induced demand can be defined as newly generated trips, but not shifted trips, by some improvements in transportation systems. This study only focused on the net induced demand rather than any other concepts belong to the general term “induced demand”. The net induced demand is quite related to the trip generation model because it refers to purely increased trips in frequency due to transportation improvement that would not be occurred without the improvement. The study analyzed trip production models with accessibility measure for each traffic analysis zone. Multiple linear regressions were adopted as the production models in the study. The study’s basic hypothesis on trip generation was that number of generated trips per day will be statistically different at different level of accessibility for each production zone. In the estimated regression model, the study considered that the parameter for accessibility, as an independent variable, can be interpreted as unit change of the net induced demand by changes of a unit of accessibility measure. This study tried to show empirically that the number of production trips was varied depending on level of accessibility for a specific traffic analysis zone with real data of household survey. The study used the 2010 household travel survey data of Daegu Metropolitan Area in South Korea with 68,398 traveler’s data. As the results, the regression analysis showed that accessibility for a specific zone significantly affected net induced demand especially for optional trip purpose. The study also showed the way how estimating quantitatively the increased net induced demand with an example.