The Kansas Department of Transportation (KDOT) and Missouri Department of Transportation (MoDOT) implemented the Kansas City (KC) Scout ramp metering pilot program to improve safety and traffic flow on a seven mile section of I-435 between Metcalf Avenue and the Three Trails Memorial Crossing. A total of seven interchanges were equipped with ramp metering systems designed to regulate on-ramp traffic volumes in response to prevailing freeway traffic conditions and reduce sudden weaving and braking movements adjacent to on-ramps to smooth traffic flow and increase throughput and safety.
The evaluation team collected traffic data in the study area before and after the ramp metering system was turned on in March 2010. The before data were collected from April 2009 to July 2009, and the after data were collected from April 2010 to July 2010.
After ramp meters were installed, transportation engineers, law enforcement officials, and Transportation Management Center (TMC) operators observed safer gaps between vehicles and fewer near miss collisions as vehicles entered the freeway.
- Initial findings from the evaluation were consistent with data collected in Milwaukee, Portland, Detroit, and Denver that show ramp metering can reduce crashes by 26 to 50 percent.
Researchers noted that the ramp metering system enabled motorists to merge more easily, move at a more consistent rate on the corridor, and experience fewer backups, secondary incidents, and congestion delay. Improvements to emergency response times were also reported. In 2009, prior to ramp metering, the average time to clear an incident was about 22 minutes on I-435 between Metcalf Avenue and 104th street. During the same months in 2010 after ramp metering was implemented, the average time to clear an incident decreased to approximately 18 minutes.
- An analysis of incident timestamps from the KC Scout advanced traffic management system (ATMS) found that the time to clear an incident decreased by four minutes after ramp metering was implemented.
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