Methods to implement geographic information systems for validation, reasonableness checks, and traffic adjustment of transportation planning models

Abstract

The current status of transportation modeling software could be best described as transitioning from software with limited visual and query abilities to travel demand models fully integrated into geographic information systems (GIS). At the same time, many analysts are waiting to see if TRANSIMS will prove to be a successful venture by the Los Alamos National Laboratories. Either way, one may expect that over time there will be a complete transition to TransCAD[Registered Trademark Symbol], UfosNet[Registered Trademark Symbol], or TRANSIMS like software. In the mean time, the material presented within this document is intended to assist those still using the more traditional travel demand modeling software. GIS has demonstrated its usefulness beyond that of data management in a variety of areas of transportation analysis. Documentation is available on the numerous interfaces that have been constructed to integrate a GIS with a modeling program in order to assist in the area of travel demand modeling. One may argue that the numerous examples of modeling-GIS interfaces that have been constructed are an indication to their usefulness and value. GIS is beneficial in performing validation and reasonableness checks. The Model Validation and Reasonableness Checking Manual and the Calibration and Adjustment of System Planning Models report include validation and reasonableness checks for socioeconomic data, network attributes and configuration, trip generation, trip distribution, mode choice, and traffic assignment. Of these various categories; input data, network attributes, and traffic assignment checks had the best fit with GIS. The use of GIS brings a time savings and graphic displays that summarize data in an easy to use format. Query and summary options assist in performing checks for either sub-areas or facility types. Likewise, GIS may be of assistance when it is necessary to adjust or refine traffic assignments. It is possible for the results from a regional travel demand model to not have the level of detail or accuracy needed in order to evaluate the impacts of a site development or corridor improvement project. Therefore, post-calibration of traffic assignments from regional travel demand models is crucial in the evaluation of such projects.