Evaluating Benefits of Systemwide Adaptive Ramp-Metering Strategy in Portland, Oregon

A systemwide adaptive ramp-metering (SWARM) system is being implemented in the Portland, Oregon, metropolitan area, replacing the previous pretimed ramp-metering system. SWARM has been deployed on six major corridors and operates during the morning and afternoon peak hours. This study entails a before and after evaluation of the benefit of the new SWARM system as compared with the pretimed system using the existing data, surveillance, and communications infrastructure. In particular, the objective of this study is to quantify the systemwide benefits in relation to savings in delay, emissions and fuel consumption, and safety improvements on and off the freeway due to the implementation of the SWARM system. A pilot study was conducted for 2 weeks on a 7-mi freeway corridor in an attempt to develop a strategic design for the future regional-level study. This paper discusses the selection process of the study corridor, the experimental design, and the results obtained from the pilot study.