As an inferno raged around them, Paradise residents fleeing the Camp Fire last year were confined to just a few escape routes, most cramming their cars down a single two-lane road in a slow-moving evacuation.

Who could get trapped in the next disaster? Residents of Pinole, Foster City, Half Moon Bay, Sausalito and American Canyon, to name a few, if nothing is done to alleviate the congestion, according to a new analysis released Thursday of small towns across the country.

Inspired in part by the traffic jams residents of Paradise faced, the study, by big data-crunching company StreetLight Data, Inc., looked only at communities of 40,000 residents or fewer to think about how traffic would flow during an emergency and spot potential bottlenecks. One researcher was looking at flows into and out of cities when he spotted a particularly bad potential traffic jam, said StreetLight Data CEO and co-founder Laura Schewel. The upcoming wildfire season was looming on his mind, she said, and a light went off in his head.

“He said, ‘Wouldn’t it be bad if everyone had to get out all at once?’ ” Schewel said. “And then we said, ‘Wait, that’s actually a thing that happens, and it’s actually a really important thing that happens.’ ”

The researchers gave scores to cities across the country based on the total population of the town, the number of roadway exits out of town, and the average number of cars each exit route carries on a typical day, assuming residents would chose familiar routes in an emergency.

Of the 30,000 communities analyzed, around 800 had scores that were three or more times the national average, including 107 in California, indicating that residents there have fewer options when it came to fleeing in a hurry. Twenty-two of the towns and cities are in the Bay Area, and one is in Santa Cruz County.

The data itself shouldn’t necessarily be taken as a prescription for county planners on what to do when they’re preparing for disasters, Schewel said. Rather, planners should think of the map as a tool to highlight areas where they might focus their efforts. But, she said, local officials will have to weigh many different factors in crafting an evacuation plan.

“Part of fire education might be reminding people they don’t have to take the main exit during an emergency,” she said, “and default behavior is not necessarily the right thing to do if you’re moving a whole city.”

Kate Miller, the executive director of the Napa Valley Transportation Authority, was facing that very prospect when she got a call the night the North Bay Fires broke out in Napa and Sonoma counties. As it happened, the winds carried the fire in such a way that they only had to evacuate portions of communities in pockets throughout the counties.

One of the places where buses were standing by to remove hospital patients was Yountville, a tiny Napa hamlet and one of the communities that ranked highest in StreetLight’s analysis of communities with few escape routes. It is also home to a veteran’s hospital and live-in facility.

Yountville is less fire-prone than Calistoga and St. Helena, so it may be have been better positioned during the fire, she said, which is spared it from mandatory evacuations. But located only 7 miles from Napa, Miller acknowledged that the town’s residents would probably face major traffic jams if everyone were to leave at once. So would everyone else in the county, she said.

“If you look at a map, it’s disturbing, actually,” Miller said. “We’re going to get stuck in this valley if something really disastrous happens.”

Planning for a large-scale evacuation in a community such as Napa County, where everyone is deposited onto the same routes, is an almost overwhelming endeavor, said Matt Wilcox, the transportation authority’s transit manager, who also sits on regional emergency planning meetings.

“The volume of traffic that would result from the style of evacuation is kind of unmanageable,” he said.

Instead, Wilcox said, the focus is often more about mass transit response and evacuating people who don’t have other means to get themselves to safety.

But if there’s a silver lining to the recent devastating and deadly wildfires, it’s having a greater sense of urgency in preparing for emergencies, said Steve Terrin, a planner and emergency coordinator with the Metropolitan Transportation Commission, a regional transportation planning agency.

The state has increased funding for workshops and regional training events, he said, leading to more sub-regional planning and the ability to focus on specific topics, such as how to manage transit for the disabled and elderly or deal with PG&E’s power shut-downs.

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Santa Clara: Crash injures one, knocks out power to hundreds The commission, in conjunction with a federally-funded regional emergency management agency, is hosting an all-day emergency planning exercise on Sept. 5 as part of an annual preparedness training drill. This year’s exercise is focused on the transportation response, Terrin said.

In those exercises, regional officials think about the types of responses needed for different types of disasters, said Randy Rentschler, a spokesman for the commission. Fires are going to warrant a much different response from floods or hurricanes, where local, state and federal authorities may have a few days of advance notice to move lots of people, he said. Similarly, the response to an earthquake would be focused on triaging the loss of life and addressing damage to roads and bridges after the fact, rather than before the disaster strikes.

“As opposed to what the federal government has in mind for much of the southeast and the south or northwest in the case of hurricanes, where they have a bit of lead time,” Rentschler said, “we aren’t afforded that luxury here.”