Evaluating Effectiveness of Ramp Meters: Evidence for the Twin Cities Ramp Meter Shut-off

Abstract

Ramp meters in the Twin Cities have been turned off for eight weeks in Fall 2000 in an experiment testing their effectiveness. This chapter analyzes the data collected during the experiment on several representative freeways during the afternoon peak period. Several performance measures for ramp metering including mobility, equity, consumers’ surplus, productivity, accessibility and travel time variation are developed and applied to the studied freeways. It is found that ramp meters are particularly helpful for long trips relative to short trips. On TH169, trips more than 3 exits in length benefit, while those 3 exits or less are hurt by ramp meters. Ramp metering, while generally beneficial to freeway mainline, may not improve trip travel times (including ramp delays). Reduction in travel time variation with the presence of ramp metering is observed as another important benefit from ramp meters. The results are mixed, suggesting a more refined ramp control algorithm which explicitly considers ramp delay is in order.