Mn/DOT Releases Ramp Meter Study Results

Public Roads, May, 2001

The Minnesota Department of Transportation (Mn/DOT) released the final results of an independent study on ramp metering in the Twin Cities metro area. Cambridge Systematics of Cambridge, Mass., evaluated the traffic flow and safety impacts associated with turning off all 430 ramp meters for six weeks last fall, as mandated by the 2000 legislature.

Results presented to Mn/DOT by Cambridge Systematics reveal that without ramp meters, there was a 9-percent reduction in freeway volume, a 22-percent increase in freeway travel times, and a 7-percent reduction in freeway speeds. The reliability of estimated freeway travel time was found to decline by 91 percent, and there was a 26-percent increase in crashes.

Market research data collection results showed a number of changes in attitude among area travelers, which occurred once meters were shut off: Most survey respondents believed that traffic conditions worsened. Support for continued shutdown remained at 20 percent. The benefit-cost ratio showed that when the costs of the entire congestion management system (including changeable message signs, traveler information, etc.) are factored in, the benefit/cost ratio for ramp metering is 5:1. When ramp meter benefits are compared to only those costs directly associated with ramp metering, the benefit/cost ratio is 15:1.