A combined distribution, hierarchical mode choice, and assignment network model with multiple user and mode classes

The traditional four-step transportation planning model, consisting of trip generation, trip distribution, modal split, and assignment stages has been used for more than four decades, and is still popular around the world. The four-step model is a top-down sequential process, in which the output from the upper stages forms the input to the lower stages. As the modeling structure is not recursive, the results obtained from the different stages might not be entirely consistent. Moreover, repeated updating and analysis of this topdown sequential process might not guarantee convergence, and hence the problem of inconsistency remains. In the last two decades, this problem has been addressed by many researchers who have sought to obtain consistent results from different stages of transportation models. Formulations have been proposed at different stages or at combinations of stages to integrate and enhance the modeling structure. This is known in the literature as the combined models.