Practical Approach to Model Trip Chaining

The need to model trip chaining has been discussed widely in the travel demand literature, but new approaches generally have been limited to academic research. Trip chaining was modeled in an actual urban area model. The model was developed for Boise, Idaho, on the basis of a household survey of 1,600 households. For this model, a tour was defined as a sequence of trip segments that start at home and end at home. The model distinguishes between two main types of tours: A tour that includes one or more work destinations is defined as a work-related tour (WRT); all other tours are defined as nonwork-related tours (NWRT). A model system was developed by assuming the hierarchy of the model components. The highest-level model estimates auto ownership for the household. On the basis of auto ownership, the frequency of WRT is estimated, and on the basis of the frequency of WRT, the frequency of NWRT is modeled. These three model components produce the number of WRT and NWRT for each household. All subsequent models are estimated at the tour level. The WRT model system includes work destination choice model, tour type model including the number of stops on the way to and from work and midday trips, and secondary destination choice model for all nonwork destinations. The NWRT model was developed in the same way with some structural differences.