Flickr/LorE Denizen

New data suggests that city population plays little role in frequency of collisions.

The more people a city has the more cars it has and the more crashes it has, right? That would seem an easy logic to believe, but according to newly released data, that assumption is wrong.

A report out from Allstate Insurance shows that the population of a city has little to no impact on the frequency of crashes that occur. The report looks at collisions and claims among its customers to determine where the most and least crashes occur in the 200 most populous cities in the U.S., though the list only includes 195 cities. (The data, collected between January 2009 and December 2010, does not include cities in Massachusetts, a state not covered by Allstate, as well as a few other areas where data was unavailable.)

The places where crashes happen the least often are Sioux Falls, South Dakota; Boise, Idaho; and Fort Collins, Colorado, where there were an average of more than 13.5 years between crashes among drivers. At the other end of the list, Washington, D.C.; Baltimore, Maryland; and Providence, Rhode Island, had the shortest gaps between crashes, at 4.7 years, 5.3 years and 5.5 years, respectively.

Among these top and bottom cities, populations range from about 146,000 to more than 619,000. That's a pretty big range. To see if there were any correlations between population size and crash occurrence, I've plotted out each of the 195 cities in the report and the average time between crashes.

New York city is the outlier way at the top, which makes it difficult to really see what's going on with the bulk of the cities with far lower populations. To get a better view, this chart shows only those cities with populations between 125,000 and 5 million.

It looks like there is somewhat of a connection between larger populations and shorter time periods between crashes. But only 9 of the 195 cities in this data set have populations above 1 million, so it's a bit disingenuous to say that larger populations definitely lead to more crashes.

So I've broken it down farther to look at just the 186 cities with populations between 125,000 and 1 million.

As you can see, there's a less distinct pattern.

Boiling down even farther, this chart shows the 162 cities with populations between 125,000 and 500,000.

The chart really starts to become a blob at this point.

And because the majority of the cities here have populations between 125,000 and 250,000, I've broken it down farther to just show how often crashes happen in this most plentiful group of 121 cities.

Again, there's no real trend to see.

This data only accounts for about 10 percent of drivers in U.S. cities, but it's still fairly representative. If these numbers are to be believed, it seems that having more people in a city doesn't necessarily mean there will be more car accidents. Exactly why people in Baltimore crash more often than people in Madison isn't clear, but the two cities' population sizes likely have little to do with it.

Image courtesy Flickr user LorE Denizen

About the Author

Nate Berg

Nate Berg is a freelance reporter and a former staff writer for CityLab. He lives in Los Angeles.

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