TRANSIMS Implementation in Chittenden County, Vermont

Abstract

To advance the state of the practice of travel forecasting, the federal government since 1992 has sponsored the development of the Transportation Analysis and Simulation System (TRANSIMS). The purpose of this paper is to describe and document experience with the implementation and calibration of the TRANSIMS model in Chittenden County, Vermont, a medium-sized urban area with a population of about 145,000. In developing the TRANSIMS model, participants in the study attempted to rely primarily on readily available data that would be easily accessible to most metropolitan planning organizations (MPOs) around the country. Following model development, several validation experiments were conducted to assess the extent to which the model after calibration replicated observed traffic counts. Preliminary sensitivity analyses were also performed to assess the sensitivity of the model results to changes in the random seed number and to evaluate the impact of changing pretimed signals to actuated controllers. The study demonstrates that the TRANSIMS Track-1 structure and the tools currently available in the model can be used to develop and calibrate a model that works reasonably well with a relatively modest effort for a small to medium-sized MPO. Moreover, for medium-sized areas with little to no congestion, the model does not appear to be sensitive to variations in the seed number, which should increase confidence in the model's results.