This paper presents the results of an effort by DKS Associates to evaluate the feasibility and impacts of freeway ramp metering on selected freeways and arterials in Contra Costa County, California. A unique feature of this study was the focus on potential impacts on arterials due to queuing on the freeway ramps and diversion to avoid the delay at the ramp meters. An important component of this project was the development of a methodology to assess traffic diversion to, from and between arterials as a result of ramp metering and to quantify the diversion impacts at selected intersections. Mitigation measures for the arterials were developed and analyzed as one method of minimizing the impacts of ramp metering. DKS used a combination of planning model runs and simulation using FREQ to identify how the ramp metering affected freeway congestion and where the ramp metering would impact arterial operation. The project was controversial for the local jurisdictions, and DKS worked closely with a Technical Advisory Committee and a Policy Committee at key points throughout the study to address key policy issues concerning the introduction of ramp metering strategies. Special methods were developed and used successfully to visually represent the location, magnitude and duration of bottlenecks and queues in the network under alternative ramp metering strategies.
Abstract