One of the important issues is that activitybased models developed in the U. S. lack an explicit linkage between household auto ownership and individual-level mode choice. Auto ownership is unquestionably a key variable in mode choice. Without explicit control over intra-household car-allocation, however, an activity-based model might inadvertently violate internal household consistency by generating more competing tours than autos yet still assign each tour to a drive alternative during the mode choice step. This potential for overestimating single-occupancy vehicle (SOV) tours will have been corrected either within the estimation process or during validation of mode choice. It is anticpated that, in the absence of a car-allocation model, household members that do not face auto shortages will come up somewhat short in terms of generating SOV tours at the aggregate level, while members of vehicle insufficient households will be producing too many SOV tours. the New York and Columbus, Ohio models is flexible enough to support explicit modeling of the intra-household car-allocation mechanism and linking mode choices made by different household members through a car-availability constraint. Within this general modeling framework, it is assumed that fully and partially joint tours (including escorting travel arrangements) are explicitly modeled at the activity generation stage. By adding a household level car allocation model towards the end of the overall model stream, are still generated the total household activities in a manner consistent with the previous modeling efforts, but explicit competition between drivers in the household over available vehicles is introduced in order to satisfy the overall household constraints on vehicles. We estimated this new type of model on the basis of a travel diary-type survey for the Atlanta, Georgia metropolitan region was estimated . The typical mode choice module is replaced with the newly estimated joint mode choice - car allocation model. This study will include some comparisons between the output of these two types of mode choice models. For the covering abstract please see ITRD E135207.
Abstract