Modeling mixed continuous and discrete corridor problems with multimodal choices

In order to investigate commuters' multimodal choice behavior on a linear travel corridor, a mixed continuous and discrete user equilibrium model is proposed in this paper. The travel corridor is assumed to connect a continuum of residential locations to the workplace. Along it, a continuum highway and a rail line with finite stations compete for traffic. In such the transportation system, commuters have four alternatives for their travel, i.e., walk, auto, walk & rail and auto & rail. The proposed model is formulated as an equivalent minimization problem, which discrete approximation version can be solved by conventional solution algorithms. Numerical results on an example corridor show that as the number of discretized sections for the corridor increases, the flow volumes gradually stabilize and hence the solution quality is improved. The proposed model can be used to explore the effect of policy changes on commuters' multimodal spatial patterns at a macroscopic level.