It has been reported that coordinating multiple ramp meters could improve the performance of ramp metering. A consulting company conducted a study for the Utah Department of Transportation (UDOT) to evaluate existing coordinated ramp metering methods and determine their applicability to the Wasatch Front region and selected the Denver Helper, Minnesota Zone, and Seattle Bottleneck algorithms as the most promising candidate algorithms. UDOT desired to evaluate the cost effectiveness of the selected algorithms against that of the local responsive ramp metering that can be implemented with the existing ramp metering infrastructure. The simulation models of the tested ramp meter algorithms were prepared using the WATSim (Wide-Area Traffic Simulation) software developed by KLD Associates for a 10-mile corridor of I-15. In total, ten WATSim simulation models were created to represent the ten cases that were evaluated--five cases for both AM and PM peak periods. Simulation analyses were conducted for the base year traffic volume (1988 volume) and for the 20-year and 40-year predicted volumes, and their results were evaluated for several measures of effectiveness. The results of the simulation analyses showed that, overall, the local-responsive ramp metering performed as effectively as the three coordinated ramp meter algorithms tested for the study site in terms of reduction in total travel time and traffic flow stabilization. Among the three coordinated ramp-metering algorithms, the Denver Helper algorithm performed best for the study site. The other two coordinated ramp-metering algorithms performed inconsistently. The performance of ramp metering is affected by various factors and the results presented in this report are site specific. Hence, additional work is needed to evaluate fully the contributions of the coordinated ramp metering methods to the entire freeway network in the Wasatch Front region. This study focused on travel time reductions and LOS stabilization of ramp metering, and the effect of ramp metering on traffic safety and the benefit of breaking up platoons of merging vehicles were not explicitly evaluated.
Abstract