NETWORK DESIGN EFFECTS OF DYNAMIC TRAFFIC ASSIGNMENT

This paper examines the effects of dynamic user-equilibrium (DUE) traf fic assignment with scheduled trip arrival times on network design out comes in comparison to outcomes with steady-state travel demands. The objective is to minimize systemwide travel cost by considering alterna tive link improvements to an existing network (e.g., select among budg et-constrained subsets of link-improvement candidates). DUE is a tempo ral generalization of static user-equilibrium (SUE) assignment with ad ditional constraints to insure temporally continuous trip paths and fi rst-in first-out (FIFO) trip ordering between all origin-destination p airs. Previous research has not investigated the effects of dynamic tr avel demands and schedule delay (i.e., shifts by trips to earlier or l ater arrival times) on network design with multiple trip origins and d estinations. DUE is formulated as a bilevel program of two subproblems solved successively by an iterative algorithm that consistently conve rges to solutions that closely satisfy the necessary optimality condit ions of this problem. Examples show the impacts of alternative combina tions of network changes affecting capacities and/or free-flow travel times (e.g., ramp metering or road widening) to depend on temporal tra vel demands and schedule delay distributions.