Alto Tunnel News Get Involved in Re-Opening Alto Tunnel

Join MCBC and the Friends of Alto Tunnel for a campaign reboot of the effort to re-open the Alto Tunnel. While important steps were taken during the 2010s, progress stalled and Marin’s electeds have felt more pressure from influential opponents of the tunnel than its supporters. It’s time to change that.

At our campaign reboot on April 8th, we brought people up to speed, explained what has been done and what still needs to happen. We also outlined opportunities on how to get involved! We also hosted a virtual Q & A on April 26. If you weren’t able to attend either event, you can find the zoom recording of the virutal Q & A here

Looking For Ways To get involved?

The Friends of Alto Tunnel is welcoming new members! We meet once a month on Zoom. If you’re interested, join one of the monthly meetings with no commitment required. Click here for details about the Re-Open Alto Tunnel Local Team

Please take 30 seconds to fill out the Alto Tunnel petition, asking our elected leaders to take the next steps to open the tunnel. 

Thank you for your interest in this important project, we hope to see you soon!

A Brief History of the Tunnel

Re-Open Alto Tunnel

Click to enlarge

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.

The opening of Cal Park Hill Tunnel, just two miles north of the Alto Tunnel, in 2010 marked a huge win, showing that the rail infrastructure of the 1800s could become the bike infrastructure of the 2000s. Today that tunnel is used by hundreds, sometimes thousands, of people a day, cutting off several miles and many minutes of travel for people traveling outside of a car.

The Alto Tunnel would open a level route separate from cars between Central and Southern Marin, saving people traveling by bike many minutes, creating an ADA-compliant route for pedestrians, and taking thousands of cars off the road as people shift their short trips to other modes.

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

We work hard to bring you the most up-to-date news about biking in Marin. We can only do this with your support. Consider making a donation today.

Support Us

sign-up for advocacy alerts

We will need your help winning these improvements! Please sign-up for advocacy alerts using the form below and we’ll tell you when/how to support our efforts.

Please enable JavaScript in your browser to complete this form.

members make it happen

We’re working to make Marin more bike-friendly for people of all ages and abilities. Are you with us?

Similar Articles

Great Redwood Trail – Closer to Becoming a Reality

Imagine yourself riding north from Larkspur Ferry, through Cal Park Hill Tunnel toward San Rafael. Three hundred and twenty miles of bike paths and trails later, you find yourself in Eureka looking out over Humboldt Bay. Sounds like a dream, right? Well, that dream took a step closer to reality this October when Governor Newsom signed the Great Redwood Trail Act (SB 69) by State Senator Mike McGuire.