The goals of ramp meters
With ramp meters, MnDOT aims to ensure that:
- Wait times are no longer than four minutes per vehicle on local ramps and two minutes per vehicle on freeway-to-freeway ramps
- Vehicles waiting at meters won't back up onto adjacent roadways
- Meter operation responds to congestion and operates only when needed
- MnDOT installed the first meters on I-35E at the entrance ramps from Maryland Ave and Wheelock Parkway in St. Paul in 1969.
- The Twin Cities Metro Area has 433 ramp meters. Some operate only in the morning peak (5:30 a.m. - 9:00 a.m.), some only during the afternoon peak (2:00 p.m. - 6:30 p.m.), and others during both peaks.
- Factors that determine the timing rates of ramp meters include congestion conditions on the freeway and real-time traffic levels on the metered ramp.
- Ramp meters react to freeway congestion conditions up to three miles from the ramp. Queue detectors help determine queue lengths and prevent long waits. Meter timing adjusts every 30 seconds.