D4 680 Field Test of Freeway Ramp Metering

Selected 4 mile section of freeway from alum Rock Avenue to Berryessa Road

Project Description

This project is to field test a new software that coordinates the timing of the ramp meters and their nearby arterial (local street) traffic signals. The test will take place in the AM peak period on I-680 between Alum Rock Ave. and Berryessa Road in the City of San Jose.

The Need

During commute hours ramp metering helps to maintain an optimum travel speed on the freeway. Traffic signals on local streets are designed to bring traffic efficiently to freeway ramps. Currently these two systems operate independently and at times can result in more vehicles arriving at the ramps than the freeway system can handle and causing undesirable operational impacts to both freeway & local streets.

The Purpose

Caltrans, UC PATH and the City of San Jose will pilot a new software that coordinates the timing of the ramp meters and traffic signals of nearby local intersections and evaluate if such a system could improve freeway operations and safety. A coordinated system would keep traffic flowing more smoothly and reducing the number of instances of traffic backing up from freeway to local streets. Key performance measures will include freeway travel time improvement, congestion duration on both freeway and local streets, frequency of vehicle backing up onto local roadway or into the intersection. During the field test, Caltrans, UC PATH, and City of San Jose will proactively monitor for traffic impact and timely mitigation.


Field Test: April 2019 thru July 2019


Victor Gauthier, Public Information Officer Santa Clara County
Caltrans | District 4
Phone No. 510-286-6115