A Model for Evaluating Integration Strategies for Operating Diamond Interchange and Ramp Metering

Diamond interchanges and their associated ramps are where the surface street arterial system and the freeway system interface. Historically, these two elements of the system have been operated with little or no coordination between the two. One danger of operating these two systems in isolation is that traffic from the ramp, particularly if it is metered, can spill back into the diamond interchange, causing it to become congested. The aim of this research was to develop integrated operational strategies for managing the diamond interchange and ramp metering operations for the purpose of improving system performances. Modeling methodologies were developed for analyzing an integrated diamond interchange - ramp metering system (IDIRMS). A computer model named DRIVE was developed, which is classified as a mesoscopic simulation model. The model was validated against the VISSIM microscopic simulation model, and researchers found general agreement between the two models. Operational characteristics were also investigated using DRIVE to gain better understanding of the system features. Integrated operational strategies were developed and evaluated under various traffic flow conditions. The analysis results indicate that with integrated operations through an adaptive signal control system, the onset of freeway congestion and breakdown is effectively postponed.