In Minneapolis-St.Paul, an evaluation of the effectiveness of ramp meters on four test corridors showed that freeway travel speeds decreased 5 to 10 percent and freeway travel times increased 5 to 10 percent between 2000 and 2001.
The evaluation was conducted in two phases:
- Phase I was designed to measure system performance, gauge public satisfaction with initial ramp metering strategies (September/October of 2000), and determine the impacts of discontinued operations during a ramp meter shut down test (October/November 2000).
- Phase II of the project was designed to optimize system performance, evaluate public opinion to alternative ramp meter strategies, and encourage long term planning (Fall 2001).
During Phase I, a variety of data were collected using multiple collection techniques including probe vehicles (operated during peak periods), traffic detectors (for traffic volume counts), traveler surveys, and crash statistics. At the conclusion of the Phase I ramp meter shut down experiment in December of 2000, the following Phase II interim ramp metering strategies were implemented:
- A number of meters were left turned off;
- Ramp meter operations were reduced to four hours each day; and
- Faster metering rates were used.
The Phase I and Phase II evaluations were conducted in a similar fashion and covered the same corridor study areas. The Phase II evaluation used field observations, focus groups, and telephone surveys to measure system performance and gauge public reaction to modified operations.
Despite the resumption of ramp metering at select locations in each corridor, traffic operations and safety performance remained degraded and were unable to be restored to pre-shut down (full metering) levels by the end of the interim period.
The following were reported in the Phase II report:
- Overall, freeway travel speeds decreased 5 to 10 percent between 2000 and 2001.
- Overall, freeway travel times increased 5 to 10 percent between 2000 and 2001.
The Phase II report ended the ramp meter study; however, the Mn/DOT will continue to monitor performance and make changes to ramp meter timing as necessary based on evolving traffic conditions.
In March of 2002, the Mn/DOT activated automated ramp meter timing systems on 30 percent of ramp meters in the study area. A traffic management center (TMC) was used to collect vehicle detector data every 30 seconds and automatically adjust ramp meter timings based on freeway conditions and changing ramp meter queue lengths. The Twin Cities automated ramp meter system was expected to be fully operational by the end of 2002.
Published By: Minnesota DOT
Prepared for the Minnesota DOT by Cambridge Systematics
Source Date: 10 May 2002URL: http://www.dot.state.mn.us/rampmeter/pdf/evalreport.pdf
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