This report provides assessments of the impact on transportation operations and a cost benefit analysis of four Advanced Traffic Management System (ATMS) components deployed in the Salt Lake Valley of Utah: incident management teams, ramp metering, signal coordination, and variable message signs. The cost analysis is based on regional value-of-time metrics.

Two of the benefits assessments in the report were drawn from field experience with the Utah system, the others were estimated using impacts derived from the literature. The benefits identified from Utah's experience with incident management and ramp metering follow:

Incident Management Team (IMT)

Incident data were collected for a duration of five years (1999-2003) for three major interstates that account for 77 percent of IMT-assisted incidents. The analysis shows that since the implementation of IMT, the average incident duration decreased by approximately 20 minutes. The decrease in incident duration was highest for incidents affecting two lanes of traffic with over a 36 percent decrease (37 minutes). Because of the increase in staff and coverage area, local IMT responses increased from approximately 2,500 incident responses in 2000 to over 5,000 incident responses in 2002.

Ramp Metering

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.