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Florida and California, two states with wide exposure to natural disasters, lack critical evacuation routes in some areas for residents to flee.
Among the 100 American communities with the most-constrained evacuation routes, 20 are in Florida and 14 in California, according to a report released Thursday by StreetLight Data Inc., which analyzes traffic patterns using data from mobile devices. Arizona ranks third with eight towns, followed by Washington and Texas with six each.
The report comes as California heads into another wildfire season with officials still sorting out the damage from the deadliest fire in state history less than a year ago, and the Atlantic hurricane season already underway in the east.
StreetLight uses machine-learning algorithms to analyze data from millions of mobile devices to help city planners and businesses better track transportation patterns and understand the infrastructure needed to prepare for emergencies.
The study was conducted on the San Francisco-based company’s platform using location data from phones and global positioning system devices, which were aggregated and normalized to show travel patterns. The evacuation-route study looked at 30,000 U.S. areas with populations under 40,000 using data collected this month.
The difficulty of evacuation was determined by what share of the population relies on one main exit for daily trips, taking into account the number of other potential routes out. A large percentage of drivers choose only one preferred route, according to the report, which examined highways, roads, dirt roads, ferries and other options.
The five most-constrained communities are islands. No. 1 is Camano, Washington, an island in Puget Sound with one bridge offering a link to the mainland. Nearby in suburban Seattle is the third-ranked town, Mercer Island, which sits in Lake Washington and is linked on two sides by Interstate 90 bridges.
Another single-bridge town, Hilton Head Island, South Carolina, ranked second. Coastal Florida rounded out the top six: Hutchinson Island South, Sanibel, and Fort Myers Beach. California communities in the top 20 included Coto de Caza and Bell Canyon.
Beyond the coasts, many of the most-constrained areas include canyons or are on lakes with minimal exit routes, according to StreetLight. The top 100 towns span 29 states.
The analysis highlights that people’s habits push them toward certain roads, which can be mitigated in advance, according to StreetLight Chief Executive Officer Laura Schewel. She said the company is working on evacuation planning with some government agencies on the gulf coast and in fire-prone regions of California.
“Even if there are seven or eight ways out of a lot of small towns, everyone prefers one, which is fine on a typical Tuesday but not if there’s an evacuation,” she said. “If everyone chooses to evacuate using one road it can be a serious problem.”
–With assistance from Alex Tanzi.