Allocation of freeway ramp metering volumes to optimize corridor performance

Abstract

A simple macroscopic freeway corridor model is formulated for the purpose of developing optimal allocations of freeway on-ramp metering volumes. The model represents a freeway and a single parallel equivalent surface street, both unidirectional, which are interconnected by freeway on-ramps. Since a choice of routes is included in the problem formulation, the fairly standard methodology of traffic is employed to predict how drivers will react to the on-ramp metering. An explicit assignment algorithm which includes ramp queueing is developed. Both the corridor and assignment models are restricted to stationary patterns. Two specific corridor performance criteria, freeway travel rate and total travel-time rate, are formulated in terms of the model variables. Then the problem of choosing ramp metering volumes to optimize a performance criterion is posed. A computationally efficient suboptimal dynamic programming scheme is developed and illustrated by an example.