In Salt Lake Valley, Utah a ramp metering study showed that with an 8 second metering cycle, mainline peak period delay decreased by 36 percent, or 54 seconds per vehicle.
The benefits of ramp metering in the region were simulated using field data from a representative site. The site was selected because it had a ramp traffic volume similar to the average ramp volume for the region. Using peak freeway traffic volumes and current metering rates from this site, a simulation was run for various metering cycle lengths. The analysis found a decrease in mainline (freeway) delay with an increase in ramp metering cycle length. For a peak-hour mainline traffic volume of 8,350 vehicles per hour and no metering, the average mainline delay was 151.2 seconds per vehicle. The greatest delay reduction, 125.3 vehicle-hours over a period of one hour, was found with an eight second metering cycle and an average mainline delay of 97.2 seconds per vehicle.
Notably, the simulation was based on variable ramp metering cycle lengths and the impact that this had on mainline traffic; it did not address delay to ramp users. The study also extrapolated this result to other ramp meter locations in the Salt Lake Valley to produce an estimate of the system-wide impact, but recommended a more detailed study to fully evaluate these benefits.
Advanced Transportation Management System Elemental Cost Benefit Assessment
Author: Perrin, Joseph, Rodrigo Disegni, and Bhargava Rama
Published By: The Utah DOT and U.S. DOT
Prepared by the University of Utah
Source Date: March 2004
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