Minnesota Department of Transportation
To help prevent traffic congestion in highway bottlenecks, Mn/DOT operates more than 400 traffic signals at highway on-ramps to approximately 210 miles of freeway in the Twin Cities metropolitan area. These ramp meters control the rate at which vehicles merge onto busy freeways during peak periods. When properly implemented and operated, ramp metering can benefit the freeway system by smoothing the overall flow of traffic, decreasing travel times and increasing safety. The objective of the ramp metering system is to improve mainline conditions while maintaining acceptable ramp queue delays and avoiding backups onto adjacent roadways.