Formulation and estimation of combined network equilibrium models with applications to Stockholm

Combined network equilibrium models of trip distribution modal split, and r oute choice are formulated and estimated for the Stockholm region. These mo dels take into account the feedback effects among three stages of the class ical four-step model. A simultaneous structure of the mode and destination choices is studied together with nested combined models reflecting conditio nal choice probabilities. In the traditional combined model, mode choice is assumed conditional on destination choice. The reverse combined model, in contrast, considers destination choice conditional on, mode choice. User-op timal traffic assignment is integrated with these approaches to modeling tr avel demand in network equilibrium models. The three combined models are es timated using the full-information maximum likelihood technique implying th at all preference parameters are estimated simultaneously. The models are e stimated on, medium-size travel and network data for the Stockholm region i n 1986. The results suggest a rejection. of the traditional nested model be cause of incorrect relative values of the estimated cost-sensitivity parame ters. The reverse nested model is preferred, even if the overall goodness-o f-fit is better for the traditional nested model. An application to a futur e; scenario for the year 2020 is included.