Supervisor Kate Sears with an update on Shoreline Highway traffic

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Dear Residents in Southern Marin:

I hear and understand the community’s frustration with traffic delays due to the more frequent traffic congestion we’ve all experienced in the Tam Junction area these many months. Thank you for writing to express your concerns and offer suggestions. I have read each and every suggestion and forwarded them to our County traffic engineer for his consideration and to share with traffic and signal engineering staff at Caltrans.

On top of our existing challenge managing traffic and bike/pedestrian flow with our new traffic lights, unseasonably good weather brought even more visitors and Bay Area local residents to Marin to enjoy the beaches and parks. As a result, we have experienced even greater traffic congestion in what would normally be our rainy, less visited “winter break.”

A number of residents have suggested removing the traffic lights altogether. Both the light at Tennessee Valley Road and the light at Flamingo were long sought by residents wanting safe passage for people walking and riding bikes. For the first time, we now have two key locations where local kids going to school, transit users, and residents going to work on foot and bike are able to safely cross a state highway in their neighborhood. Let’s give this safe crossing a chance.

Marin County Public Works and Caltrans are continuing to work to adjust signal timing at the Tennessee Valley Road/SR 1 intersection and to reduce travel times along the State Route 1 corridor.


In late November, the County Department of Public Works (DPW) restriped the Tennessee Valley Road approach to the intersection with State Route 1 to allow room for right-turning vehicles to turn separately from the left-turning vehicles. Caltrans also revised the signal timing to improve traffic flow.

In November and December, we received many reports of significant delays (some upwards of 20 minutes) along the route out of Mill Valley and Tam Valley. County Public Works staff drove these routes in November and December to note the times experiencing the most significant delays. DPW verified your reports of delay. With some changes in signal timing and with the restriping at Tennessee Valley Road, those delays were reduced during the morning peak (from 8:00 am to 8:45 am) from a high of 20 minutes to approximately 9 to 11 minutes.

More recently, in the first two weeks of January, Caltrans staff conducted additional field reviews to identify further signal timing adjustments and other possible strategies to reduce delays. As a result, Caltrans has recommended the installation of separate right-turn signal heads at the Tennessee Valley Road approach to Shoreline Highway to better control the right turn movement there. County staff has received a bid from a contractor to install these signal heads and will be working to identify funding for their installation.


County DPW has contracted with W-Trans, a private transportation consulting firm, to assist Caltrans in providing the most effective signal timing. The W-Trans traffic signal expert is scheduled to observe traffic and traffic signal operations during the second week in February.

We look forward to receiving W-Trans’ recommendations for signal timing adjustments and any potential improvements to reduce travel times in the corridor.


Thank you for sharing your observations and many thoughtful suggestions, and for your patience in getting through this difficult transition. We will continue working to resolve these traffic congestion and light timing issues in a way that helps restore smoother traffic flow for all users – motorists, cyclists, transit users and pedestrians.

As always, feel free to write to me at or call 473-7331.

Thanks for your attention to this message.