Abstract
In this paper, the problem that consists of the four travel choices (i.e., trip generation, trip distribution, modal split, and traffic assignment) with variable demand is deliberately formulated as a non-linear mathematical model. The associated optimality conditions are presented. A heuristic solution algorithm that adopts combined model concept was proposed. By way of supernetwork techniques, each combined model can be addressed as an “extended” traffic assignment problem and solved using any available traffic assignment solution algorithm. As compared with the traditional four-step travel demand forecasting procedure, this heuristic has advantage of considering the travelers' travel behavior throughout the solution procedure and hence more suitable to be applied to the transportation planning applications in the real world.
