Alto Tunnel News Advocacy Pushes Tunnel Project Back on Track

The Alto Tunnel isn’t a new project but thanks to the efforts of MCBC and the Friends of Alto Tunnel, it’s been gaining fresh momentum as advocacy efforts over the last year have revived a project that had lost energy during the pandemic.

In April 2023 we hosted the Alto Tunnel Campaign Reboot to a great turnout and much excitement. Since that launch party, MCBC and the volunteers from Friends of Alto Tunnel have been busy pushing the tunnel float through parades, tabling at local events and along the Mill Valley Sausalito Pathway, and collecting signatures on our petition. Last week, along with nearly two dozen volunteer speakers, we presented the Marin County Board of Supervisors with our petition, signed by over 2,000, asking for work on the tunnel to continue.

Tarrell Kullaway and Don Herzog with the petition in front of Marin Board of Supervisors Room

Tarrell Kullaway (MCBC) and Don Herzog (Friends of Alto Tunnel) hold the petition signed by over 2,000 Alto Tunnel Supporters. March 19, 2024.

Alto Tunnel: A Brief History

For those less familiar with the project, the Alto Tunnel is a late-1800s railroad tunnel that has been shuttered since 1971 and now sits partially collapsed awaiting its final fate; total collapse or renewed life as a key part of the long-awaited North-South Greenway.  

The Alto Tunnel will connect Mill Valley to Corte Madera, and complete a greenway from southern to northern Marin, enabling people of all ages and abilities, whatever their purpose – commuting, transportation, exercise, recreation – to walk, bike, and roll safely and efficiently, enjoying the beauty of our communities for generations to come.

-Vision Statement, Friends of Alto Tunnel 

Opening the Tunnel would also remove an estimated 2,000 cars off the road per day, reducing greenhouse gas emissions and alleviating the frustration of traffic jams for those who drive. 

Back on Track: Presenting to the Board of Supervisors

On Tuesday, March 19th, MCBC and the Friends of Alto Tunnel presented a petition with over 2,000 signatures along with a letter of support co-signed by two dozen organizations and businesses, to the Marin County Board of Supervisors. We’re grateful for the tremendous showing of support from community members who signed and shared the petition, as well as Marin Cyclists and many other local businesses and bike shops who signed the letter of support. 

The Board of Supervisors meeting drew numerous supporters to give their comments both in person and online, all with a unique take on how a reopened Alto Tunnel would benefit their communities. Read on to hear what some of our advocates had to say, and you can watch the Board of Supervisors meeting here

No other project before you right now has the potential to save emissions like this project couldI believe we have the courage in this room to take the next step – yes, there will be issues, but let’s prioritize working through them. Like no other time in our history, money is coming down from the feds for exactly these types of projects. Would we rather the money be spent in another county or here?  By not asking, we will never receive. – Tarrell Kullaway, Executive Director of MCBC and Vice Mayor Town of San Anselmo

Alto Tunnel meeting

Advocates for a reopened Alto Tunnel speak to the Marin County Board of Supervisors. March 19, 2024.

As a kid growing up in Tiburon, my bicycle was my source of freedom…Now, 50 years later, I still have the desire to roam freely as I once did on my bicycle. But I’ve lost the use of my legs due to ALS. If the Alto Tunnel was a reality,  I could safely use bike paths as a flat route to Mill Valley, Sausalito, and Tiburon once again, this time on my wheelchair. I urge you to consider taking the steps needed to bring this valuable resource to our community. – Miles McConnell

Re-Open Alto Tunnel

Click to enlarge

… to actually accommodate the people who want to ride, we need to provide safe and separate places for them to do so. Studies have shown, and common sense confirms, that elderly adults or parents traveling with children do not want to share the road with cars…they need and will readily use multi-use paths….please consider funding an environmental impact report for reopening this critical gap in Marin’s North-South Greenway. – Lee Larsen, Friends of Alto Tunnel


Keeping the Momentum

There’s still more work to be done. Along with our supporters and fellow advocates, we will continue to reach out to the County of Marin, as well as staff and councils of Mill Valley and Corte Madera. We will continue to collect signatures on the petition (it’s not too late to show your support!), and if we have to show up next year with four thousand signatures for our voice to be heard, so be it. With a project this big our work is far from over, but we believe that together, we can make it happen. 

Learn more about the Alto Tunnel at

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Get Involved in Re-Opening Alto Tunnel

The single most transformative project in Marin County would be the re-opening of the Alto Tunnel to bicycle and pedestrian travel. The tunnel, dug through the ridge between Mill Valley and Corte Madera by the Northwestern Pacific Railroad in 1884, was boarded up in 1975. But since the 90s, advocates have pushed to repurpose the Alto Tunnel, and other tunnels like it, for active transportation use, allowing people to bypass hills and avoid busy roads.