Alto Tunnel News Alto Tunnel Campaign Update – Winter 2024

The Friends of Alto Tunnel are hard at work advocating for the reopening of Marin’s second rail tunnel-to-trail! We’re back to share some of the updates from our last few months of work. 

Alto Tunnel Campaign Updates

Dad riding through tunnel float with kid on cargo bike

Community Canvassing

Our volunteers went out in the community a number of times last summer and fall to educate people about the existence and benefits of the tunnel, and to collect additional signatures for our petition. See below for some photos from Corte Madera’s 4th of July parade, International Walk and Roll to School Day, MCBC’s Biketoberfest, and various days tabling on Marin’s multiuse pathways. If you see us out there, say hi!


The petition to move the Alto Tunnel to preliminary design and environmental review has collected more than 1,800 signatures, 90% of our goal! Over 1/3rd of the signatures are from residents of Mill Valley or Corte Madera, representing hundreds of people. If you haven’t signed it yet, click here to fill it out! Once we hit our goal, we will present it to the Marin County Board of Supervisors. Share it with friends and family to help us achieve (and exceed) our goal!Two volunteers at MCBC's Octoberfest holding "Local Teams" sign


In addition to the petition, the effort to open the tunnel has been joined by a host of advocacy organizations, environmental groups, local businesses, and riding groups. Over a dozen organizations have joined our sign-on letter, which you can read here. If you represent a group that is potentially interested in co-signing our letter, please email We’re happy to give a brief presentation to any board members or decision-making body!

Residents Speak to the Need

Hikers may be interested in trekking over Camino Alto, but people who want to get to Mill Valley on foot aren’t going to take on that challenge. Walkers coming from Sausalito don’t think about heading to Corte Madera or places north on foot; the hill facing them is too much of a deterrent. But reopening the Alto Tunnel will give walkers a flat, safe and accessible route. It will reduce driving and reduce traffic and our carbon footprint. 

We’ve been talking to people on both sides of the hill about how much better their lives could be if the tunnel were open to bike and pedestrian travel. We asked a Corte Madera resident who walks regularly for exercise if she walks to Mill Valley or places south. Here’s what she said.

I love walking. And I like walking on a path whenever possible; it’s safer and quieter than being on a street. I wouldn’t consider walking over the hill to go south, but if the tunnel reopened, I would definitely use it. 

And here’s what a Redwood student told us about his experience recently returning from Sausalito with his bike after working late. Typically he puts his bike on the bus, rides to Corte Madera and then bikes home to Ross. But on this dark and rainy night, there was no room for his bike on the bus. He said,

My only option was to ride over Horse Hill; It was NOT a good experience. The Alto Tunnel would have made things so much easier for me! The tunnel would shorten the ride and I might not need the bus at all.

How You Can Help

Re-Open Alto Tunnel

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Join Friends of Alto Tunnel

Friends of Alto Tunnel is the volunteer group supported by MCBC that organizes the campaign to reopen the tunnel. We meet monthly, typically on Zoom and occasionally in person in Mill Valley. 

The group’s next full meeting will be on Monday, February 5th at 3 pm. Register here on Zoom.

For more information about the studies done up to this point, please visit the Friends of Alto Tunnel website at

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