New Methods for Improving Non-Home-Based Trips in Trip-Based Models

As part of a study by the Federal Highway Administration (FHWA) Travel Model Improvement Program (TMIP), new incremental improvements were made to the Salt Lake City metropolitan area’s trip-based travel model to improve the handling of non-home-based trips. These techniques are designed to be inexpensive enhancements to existing trip-based models that can be implemented quickly in a straightforward manner as part of a model update without requiring the development of a whole new model. The new methods are intended to address fundamental problems with the accuracy and response properties of non-home-based trips in trip-based models. These problems can be understood in a variety of ways, but ultimately are related to the inconsistency of the four-step model with tours. The fundamental approach to addressing these issues in the methods tested is to adopt an alternative trip-based model architecture in which non-home-based generation and distribution models are run in series rather than in parallel with home-based component models. This relatively simple structural change appears to significantly improve the trip-based model’s ability to represent non-home-based trips and their response to land use changes and transportation infrastructure investments.