BRAESS'S PARADOXES IN DYNAMIC TRAFFIC ASSIGNMENT WITH SIMULTANEOUS DEPARTURE TIME AND ROUTE CHOICES

Abstract

In this paper, we investigate some new dynamic phenomena of Braess's paradox in transportation networks when both the departure time and route choices are considered simultaneously. The classical Wardropian user equilibrium principle is used to characterize route choice behavior, and the traditional bottleneck models with deterministic queues are employed to describe user's departure time choice behavior. New Braess's paradoxes with dynamic user response have been found in respect to the point queue and physical queue assumptions, and the mechanisms of such paradoxes are analyzed in details. Furthermore, it is shown in a numerical example that a paradox may occur in network when physical queue assumption is made, but the paradox may not be found in network if the point queue assumption is adopted in the proposed dynamic traffic assignment model. Due to the significant difference between point queue and physical queue assumptions, spatial dimension of queues has to be considered carefully in dynamic traffic assignment models. Finally, some traffic management measures are suggested and examined to resolve the potential paradoxes, such as link closing, ramp metering, dynamic road pricing, lane partitioning, and adaptive traffic control etc.

Keywords:

• Braess's paradox
• simultaneous departure time and route choices
• dynamic user equilibrium
• bottleneck
• queue spillover