The Most ‘Evacuation-Challenged’ Communities in the U.S.

StreetLight Data analyzed 100 communities and compiled a list of areas in the country with limited evacuation routes. The data is free and can aid neighborhoods in planning for evacuation or developing infrastructure.

by Jim McKay / August 27, 2019
Cars are backed up on Bridge Street in LaBelle, Fla., heading north Friday, Sept. 8, 2017. Increased traffic in the quiet town was due to Hurricane Irma evacuations, according to locals. AP

Evacuation planning is one of the most difficult tasks in emergency management, and on evacuation routes, bottlenecks in recent disasters have resulted in loss of life.

That was the impetus for StreetLight Data to conduct a national (plus Canada) analysis of small towns and their evacuation risks in situations like floods, fire, dam breaks, hurricanes, tornadoes and other emergencies.

The results are available for free to government agencies looking to develop disaster evacuation plans or develop improved infrastructure.
The analysis looked at 30,000 towns in the United States with populations under 40,000 and with the results of the analysis, StreetLight Data compiled a list of the most “evacuation-challenged communities.”

The states with the most evacuation-challenged communities are:

1.    Florida (20 communities)
2.    California (14)
3.    Arizona (8)
4.    Texas (6)
5.    Washington (6)

“We were developing some cool visualizations about traffic flow, and our CTO saw there was one area where traffic flowed from just one area and thought, ‘That would be tough if everyone had to leave at the same time,’” said StreetLight Data CEO Laura Schewel. “That was the genesis for the study.”

“So we developed some tools to show these ‘car sheds’ of driving,” she said. “We decided to analyze small towns because those are the ones where you get the most horror stories and they have the most bottlenecks and the least amount of resources to deal with it.”

Schewel’s team developed an index that looked at a few factors to assess evacuation constraint risk. The first factor is how many total routes out of town there are. Another is, on a typical day, what percentage of people take a certain route, even if there are multiple routes. The last factor was total population.

Even though there may be more than one route out of town, many people would choose a certain route out of ease of use or habit. That’s an important factor to know for an emergency manager who is thinking about ordering evacuation. It might prompt an earlier evacuation or calls to use a different route.

Or there may be four routes out of town but three are terrible roads, so 80 percent of the population will seek to travel on that own road. “What we hope is that this data escalates a conversation with authorities to talk about evacuation planning in a more pointed way,” Schewel said.

Schewel said the company can also do more rigorous studies for more in-depth transportation planning purposes as well. For example, “How does this part of town differ from another part of town or how is it different in winter and summer?”

The company uses proprietary data processing engine that collects millions of location points from smartphones and GPS navigation devices in autos, and transforms them into contextualized, aggregated travel patterns. It then develops a “main exit load” percentage from the percentage of the population’s daily trips that take a main exit.

“We also process Internet of Things data from sensors from things like weigh stations for trucks,” Schewel said. “And we turn it into an accurate and aggregated description of what’s happening on any road, neighborhood bike lane, offramp, or block in the United States or Canada.”
Here are the top 20 U.S. communities with the most constrained evacuation routes:

1.    Camano, Wash.
2.    Hilton Head Island, S.C.
3.    Mercer Island, Wash.
4.    Hutchinson Island, Fla.
5.    Sanibel, Fla.
6.    Fort Myers Beach, Fla.
7.    Carpendale, W. Va.
8.    Pahrump, Nev.
9.    Nahant, Mass.
10.    Skidaway Island, Ga.
11.    North Bay Village, Fla.
12.    South Beach, Fla.
13.    Coto de Caza, Calif.
14.    Golden Beach, Md.
15.    Six Shooter Canyon, Ariz.
16.    Immokalee, Fla.
17.    Hoyt Lakes, Minn.
18.    Bell Canyon, Calif.
19.    Long Beach, N.Y.
20.    Siesta Key, Fla.
 

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