Ramp Meters on Trial: Evidence from the Twin Cities Ramp Meters Shut-off

Ramp meters in the Twin Cities have been the subject of a recent test of their effectiveness, involving turning them off for 8 weeks. This paper analyzes the results with and without ramp metering for several representative freeways during the afternoon peak period, depending on data availability. Seven performance measures: accessibility, mobility, equity, productivity, consumer surplus, travel time variation and travel demand responses are compared. It is found that ramp meters are particularly helpful for long trips relative to short trips. On Route 169, 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 segments, may not improve trip travel times (including ramp delays). Travel time variation is reduced as another benefit from ramp meters. Non-work trips and work trips do respond to ramp meters, but via different ways. The results are mixed, suggesting a more refined ramp control algorithm which explicitly considers ramp delay is in order.