Ramp Metering and On-ramp Widening at the East Blithedale Avenue/Tiburon Boulevard/Hwy 101 Interchange

Modifications expected to help ease congestion on East Blithedale

April 24, 2019

Beginning this month, Caltrans is installing ramp meters in two phases in Marin County. Phase 1 includes construction of ramp meters in the northbound direction along Highway 101 from Spencer Avenue to Sir Francis Drake Boulevard. The project will also create a two-lane northbound on-ramp to highway 101 at Tiburon Boulevard with related access improvements.

Representatives from Transportaion Authority of Marin and Caltrans recently updated the City Council on the topic at their May 6, 2019 meeting. 

Read the Staff Report | Watch the update (jump to Item 2).

The Mill Valley City Council announced the widening project in 2017 to reduce congestion leading to the 101 freeway from both Mill Valley and the Tiburon Peninsula.

“When Caltrans first began discussing their plans for ramp metering along the 101 Highway corridor, we saw the opportunity to improve the traffic backup motorists experience when exiting Mill Valley towards the East Blithedale overpass interchange,” Councilmember John McCauley said.

The City, having studied the traffic problem for some time, determined that traffic from the Redwood Highway Frontage Road headed north to the Highway 101 freeway onramp or west into Mill Valley represented 15% of all traffic movements but consumed 35% of the “green time” – the length of a green traffic signal. Traffic engineers established that widening the Highway 101 northbound onramp would allow these cars to progress more quickly, reducing their green time and allowing more movement east-west on the overpass.

“We fought hard and successfully to get Caltrans to widen the northbound onramp so that frontage road traffic could proceed to the freeway faster,” McCauley said. “This change will allow more east-west green time which is projected to help relieve the backup out of town.”

The project includes new ramp metering lights on the Highway 101 onramps from East Blithedale Ave and Tiburon Boulevard (heading north).  Phase two will complete metering of the remainder of the northbound on-ramps and will install and activate the southbound on-ramp meters. Work on these two onramps includes widening and installation of Traffic Operations Systems (including ramp meters).

Work will include occasional ramp closures and detours. Ramp closures will occur at night to reduce traffic impacts. Construction activities will last about a year and the meters will be activated in the spring 2020.

Please click here for the Caltrans Ramp Metering Fact Sheet

About Ramp Metering

Ramp metering manages traffic entering a freeway by regulating the flow of traffic and making it smoother for vehicles to merge onto the freeway.

The Ramp Metering Program is part of the larger Freeway Performance Initiative, a partnership between the Metropolitan Transportation Commission (MTC), Caltrans and local congestion management agencies. The initiative works to apply technology to reduce the effects of congestion, including ramp metering, message signs, roving tow trucks to clear incidents, and 511 traveler information.

A Ramp Metering Technical Advisory Committee (RMTAC), was formed by MTC, Caltrans, Transportation Authority of Marin, Marin cities and towns, and the County of Marin, to provide direction for the Ramp Metering Program.


Video that provides an overview of Ramp Metering in Marin County.

Fact Sheet: The benefits of ramp metering and how metering works.

Additional Resources.

Public Outreach

Transportation Authority of Marin has previously presented the metering project and benefits to multiple community groups including a workshop in Mill Valley. The list below is not comprehensive, but highlights key meetings and resources for additional information.





Mill Valley City CouncilMay 6, 2019Mill ValleyStaff Report

Transportation Authority of Marin Board

February 28, 2019

San Rafael

Staff Report


Mill Valley City Council

August 3, 2015

Mill Valley

City Manager’s Report

Mill Valley City Council

January 20, 2015

Mill Valley

Staff Report

Strawberry Recreation District Board

October 8, 2014

Strawberry/Mill Valley

Transportation Authority of Marin Board

October 23, 2014

San Rafael


General Public

November 20, 2014

Mill Valley Community Center


Questions or comments – Please contact:

Vince Jacala
CalTrans Branch Chief
Phone: (510) 286-5206

Andrew Poster
Mill Valley Public Works Director
Phone: (415) 384-4800