Using Archived ITS Data to Measure the Operational Benefits of a System-wide Adaptive Ramp Metering System

The current ramp metering strategy in Portland employs a pre-timed algorithm that determines the times that the meters are active as well as each ramp’s metering rate. As part of the original ramp metering deployment, a surveillance system, including inductive loop detectors and closed circuit television (CCTV) systems, is in place. Starting in May 2005 a system-wide adaptive ramp metering (SWARM) system is being implemented in the Portland metropolitan area and should be operational on all corridors by April 2006. Portland State University has implemented the Portland Oregon Transportation Archive Listing (PORTAL) which archives the freeway loop detector data at…

The current ramp metering strategy in Portland employs a pre-timed algorithm that determines the times that the meters are active as well as each ramp’s metering rate.  As part of the original ramp metering deployment, a surveillance system, including inductive loop detectors and closed circuit television (CCTV) systems, is in place. Starting in May 2005 a system-wide adaptive ramp metering (SWARM) system is being implemented in the Portland metropolitan area and should be operational on all corridors by April 2006. Portland State University has implemented the Portland Oregon Transportation Archive Listing (PORTAL) which archives the freeway loop detector data at its most detailed level. While the SWARM system is designed to be more effective than the current ramp metering strategy, the true benefits of the new system have not yet been quantified. Using an existing data stream, there is a unique opportunity to conduct a true before and after evaluation of the operational benefits of the new SWARM system. This will aid in the optimal deployment of current SWARM system and will be transferable to other regions as their systems come on line in the future. The project will also develop an interactive simulation laboratory for evaluating and improving the new SWARM ramp metering system in the Portland metropolitan area. The simulation laboratory will be based on VISSIM, a microscopic traffic simulator currently used by ODOT for certain traffic studies. Freeway geometry, traffic demand, vehicle performance, and driver characteristic models in the simulation laboratory will be calibrated and validated based on the PSU PORTAL database for the freeway corridors selected for the field experiment. The simulation-based evaluation will help confirm field experiment results, and complement the field experiment by testing alternative solutions to any operational issues identified during the field experiment. This project will also test different control parameters in the SWARM algorithm, and recommend strategies for improving the algorithm.