Twin Cities Metro Area Ramp Meter Study
Results presented to MnDOT by Cambridge Systematics showed that without ramp meters there was:
- A 9 percent reduction in freeway volume.
- A 22 percent increase in freeway travel times.
- A 7 percent reduction in freeway speeds, which contributed to the negative effect on freeway travel times. The reliability of freeway travel time was found to decline by 91 percent without ramp meters.
- A 26 percent increase in crashes, which was averaged for seasonal variations. These crashes broke down to a 14.6 percent increase in rear-end crashes, a 200 percent increase in side-swipe crashes, a 60 percent increase in "run off the road" crashes, and an 8.6 percent increase in other types of crashes.
Market research data collection results showed a number of changes in attitudes among area travelers that occurred once meters were shut off, including:
- Most survey respondents believed that traffic conditions worsened.
- Support for modification of the metering system increased from 60 to 70 percent of respondents, and included such changes as using faster cycle times, having shorter operating hours, and using fewer meters.
In 2002, MnDOT launched its new responsive ramp meter timing system to:
- Reduce delays caused by congestion and crashes.
- Reduce the number of crashes caused by congestion.
- Provide travelers with more reliable travel times.
- Manage ramp meter wait times.
A key aspect of the new system was the addition of automated monitoring of wait times at meters so they can be adjusted as needed by MnDOT's traffic management center computers. The system provides real-time information about ramp delays and limits wait times based on ramp conditions as well as freeway conditions. Specific system features include:
- Ramp meter waits will be no more than four minutes on local ramps and no more than two minutes on freeway-to-freeway ramps.
- Vehicles waiting at meters will not back up onto adjacent roadways.
- Meter operation will respond to congestion and only operate when needed.
Public involvement a key contributor
Throughout the study process, MnDOT sought guidance from a Citizens Advisory and a Technical Committee. Both were charged with representing the public and ensuring the credibility and objectivity of the study. Committees provided policy oversight, technical guidance, expertise and quality control.
Additionally, a series of focus groups and telephone surveys measured customer satisfaction. These captured traveler-oriented perspectives from 1,540 individual users regarding ramp meters and ramp meter operations.