Synthetic models for through trips in small urban areas

This research studied the usefulness of using synthetic models for through trip end estimation and distribution for small urban areas. Three sets of models--NCl, NC2, and KY--which were previously developed in North Carolina and Kentucky respectively were evaluated as a part of this study. All the three models were essentially two stage models. The first stage estimated the number of through trip ends at each Cordon station. The second stage distributed the through trip ends calculated in the stage one from each origin station to all other destination stations.

The basic features of all the models were compared to bring out their similarities and differences. The models were then tested with the help of data obtained from fourteen small urban areas in North Carolina. The trip end estimation stage was tested on all the fourteen urban areas and the trip distribution stage was tested on six of these urban areas. Later the estimated through trips were compared with the actual through trips obtained from 0-0 surveys to assess the accuracy of the models. RMS and percent RMS errors were calculated to measure the extent of the deviation. The models were applied and tested using a computer program.

Based on their performance the models were ranked in order of preference. It was found that the NCI model performed better than the other two models in predicting the through trip flows. An analysis was performed to determine the sensitivity of functional classification for all the three models, and the sensitivity of route continuity on the NC2 model. The results obtained showed that the NCI Model was the most sensitive to changes in functional classification. Further it was observed that all three models were more sensitive to changes with respect to a higher level functional classification compared to a change of a lower level functional classification. A similar pattern was also observed for sensitivity to changes in route continuity.

The accuracy of the models in predicting large volumes of through trips was found to be acceptable. It was finally concluded that the models could be used as an useful tool for quick estimation of through trip patterns in a small urban area.