Take one car: the math behind Mill Valley's evacuation plan

What's happening: Monday's fire on Hillside Avenue was small, contained by evening, and never triggered an evacuation order. But it's a good moment to explain what the city is actually asking residents to do before a bigger one comes, and why.

The context: In 2023, Google Research ran a citywide traffic simulation for Mill Valley, modeling how long it would take every household to get out ahead of a wildfire. Mill Valley has about 11,400 households and, at two cars each, as many as 22,800 vehicles that could try to leave at once, all funneled onto four lanes leading to Highway 101.

Researchers Damien Pierce and Yi-fan Chen modeled how much extra time traffic congestion adds to an evacuation under the city's adopted plan, on top of however long it takes people to get in their cars and start driving.

At two cars per household, congestion adds 2.7 hours. At one car, it adds only 1.1 hours, a savings of roughly an hour and 36 minutes, more than half the time. Former Mill Valley Mayor John McCauley, who spearheaded the research, described the math to the council more plainly: with a fixed number of lanes out of town, "please, please, please take one car" moves everyone else faster, not just the household that complies.

Plan A, the third way out: Mill Valley funnels evacuating traffic toward three sets of highway on-ramps. Two are the ones most residents already think of: the northern ramps, reached via E Blithedale Ave, and the southern ramps near Tam Junction, reached via Miller Ave. The third, near Hamilton Drive, isn't normally an option at all, since Hamilton runs one-way back into town.

The city's plan reverses a stretch during an evacuation and reroutes some cars off East Blithedale Ave onto Roque Moraes Drive, past Hauke Park, to reach it. Opening that route is the single biggest fix in the city's plan: the study found it cuts total evacuation time by close to two hours, a reduction of more than 40%, on top of whatever savings come from taking one car instead of two.

Reaching that highway ramp isn't the same as reaching safety, either. At 1.5 cars per household, the study found that under the adopted plan, nearly the entire city reaches the flatter, lower-risk part of town within three hours, even before every car has made it onto the highway.

Plan B, the Super CRAs: If the roads back up anyway because of Highway 101 traffic, the city has a second tool. Bayfront Park and Tamalpais High School are designated Super Community Refuge Areas (CRA), large open lots that can be filled quickly with cars pulled off the roadway, packed tightly, holding roughly 4,000 vehicles. It allows authorities to get vehicles clogging the roads out of the way so residents still coming down from the hills can keep moving.

In a September 2021 drill, the city queued cars on E Blithedale Ave and moved them to the refuge area at Bayfront Park. The drill cleared 250 cars in just 19 minutes.

Why it matters: In April 2025, a larger drill tested Plan A directly, sending cars from Miller Avenue through Camino Alto and E Blithedale Ave to the underused on-ramp near Hamilton Drive. McCauley called the drill a success. It was significant enough that FEMA and the US Fire Administration picked Mill Valley as one of three communities nationally for a tabletop exercise beforehand, meant to help write evacuation guidance for other towns.

Where things stand: Police Chief Rick Navarro told the Briefing the city has finished nearly everything on its list, including live-feed evacuation cameras and signage for its regular refuge areas. The one piece still in progress, he said, is the signage for the Super CRAs. “The Super CRA signage remains a priority to ensure our evacuation plan is fully implemented and operating as intended,” Chief Navarro told the Briefing.

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A new countywide survey has found that Marin residents are having a harder time finding local news than researchers have seen almost anywhere else they have studied this year.

Just over half of the 832 adults surveyed by Embold Research said it is difficult to find news about their own city or town, compared with only 21% who said the same about national news. The Civic Information Needs Census, done in partnership with the Bay Area nonprofit publisher Cityside, put the margin of error at 3.6%.

Eric Newton's reporting for Local News Matters fills in what the numbers mean for Marin. He found that satisfaction splits sharply by topic and by age, that confidence in dealing with local government varies by ethnicity and education. Read his full piece at Local News Matters.

Friday, July 31

🎬 Summer Movie Series: Happy Feet, Mill Valley Public Library, 3-4:30pm. Head to the Creekside Room at 375 Throckmorton Ave for a free family screening of Happy Feet, following Mumble's tap-dancing adventures across Antarctica. Free entry; no registration required.