Are Some Cities Built to Encourage Drunk Driving?
After last week’s geography of drunk driving post, a number of readers were eager to see more specific data relating to cities.
The author of that map, John Nelson of IDV Solutions' UX blog, has been at work on that very issue. Using the same Fatality Analysis Reporting System data of fatal car crashes from 2001 to 2010, Nelson ran the numbers for the 25 most populous U.S. cities, with fatal car accidents measured against population.
A teaser: the American city with the lowest percentage of fatal crashes involving intoxication is Birmingham, Alabama, where only 13.6 percent of fatal crashes were substance-related. The city with the highest is Stamford, Connecticut, where 55.8 percent of fatal crashes involve intoxication.
The bulk of the data, though, involves the 25 largest U.S. cities, sorted in a chart by four different metrics:
- The 25 Most Populous Cities in the United States
- Fatal Traffic Crashes per 1,000 People
- Fatal Traffic Crashes Involving Intoxication per 1,000 People
- Rate of Fatal Crashes Involving Intoxication
Due to its size, we can't display the full image here without compromising its legibility. You can follow along on a stand-alone image here, or check out columns two, three, and four below:
We find, essentially, three categories of cities.
1. Relatively safe cities for driving
New York City and Philadelphia are the biggest ones in this category, but there are a number of smaller municipalities that also qualify – Baltimore, Washington D.C., Boston, and San Francisco. They have a low number of fatal car accidents per capita, a low number of fatal accidents per capita involving intoxication, and the percentage of fatal accidents that involve alcohol is also low.
2. Across-the-board dangerous cities for driving
The roads of Houston, Phoenix, Dallas, and Jacksonville all seem like great places to avoid. Statistically, these are some of the least safe large cities for driving in the United States. Between 2001 and 2010, each of them had a rate of fatal car accidents higher than one per thousand residents (see excerpt from column 2, below left). They also had very high rates of fatalities involving intoxication.
But now is a good time to point out a caveat: these per capita statistics weigh accidents within city lines against city population, as an approximate indicator of how many people are driving. This makes some cities look deceptively small, though as anchors of metro areas they contain a much larger number of drivers, many of whom commute in and out of the city. Since the population of many cities -- L.A., Houston, Phoenix, San Diego, etc. -- hovers at around one-third that of their metro area, the effect is pretty evenly distributed.
But there are exceptions, like Detroit. Though it has the most fatal accidents per thousand residents with intoxication (column three) and without (column two), Detroit's dwindling population is only one-sixth that of its metro area. So if statistics were adjusted for metro area size to better approximate the number of drivers, Detroit would drop significantly on that list. There's a similarly small ratio for D.C. and Boston. Given the number of non-resident drivers moving through these cities, they are a bit safer than they appear on this list.
This point may be made in reverse about Jacksonville, whose sprawling city limits include over half the population of the metro area. Thus, compared to its neighbors at the top of the list -- Houston, Phoenix, Dallas, and especially Detroit, all of which deal with a huge number of non-resident drivers -- Jacksonville's streets are even more deadly than that fatalities per capita figure would have you believe.
3. Cities whose roads are generally safe, but with high rates of drunk driving
The fourth column indicates the percentage of fatal crashes that involved intoxication, also understood as the ratio of columns two and three. At right, an excerpt, 3-10 (Denver is 1, Houston 2):
Here lie some of the chart's most interesting findings. Many cities, from the safe-driving (NYC, Boston) to the not-so-safe-driving (Phoenix, Houston) have similar positions in all three lists. But not all.
Some cities with fewer fatalities per capita (low in columns two, three) move sharply up the table in column four. Consider Seattle, Chicago, San Jose and San Diego. They are all in the bottom ten for fatalities per capita. A large percentage of those fatalities, though, involve alcohol, putting them in the top ten for rates of fatal accidents where intoxication was involved. (Denver rockets right to the top of column four, the only major U.S. city where over half of fatal accidents involve intoxication. But it has a relatively high rate of fatalities per person without intoxication, too.)
There's a strong division, in other words, between the ten cities on the list where fatal accidents are the least common. Six of them -- NYC, Boston, Baltimore, SF, Washington D.C., and Philadelphia -- remain in the bottom ten of column four, with low rates of fatal crashes involving intoxication. But Seattle, Chicago, San Jose and San Diego shoot into the top ten. What characteristics distinguish the former from the latter? Design? Geography? Culture?
Memphis is a bizarre outlier here, 3rd in fatal crashes per capita, but 18th in fatal crashes involving intoxication per capita. Measured by percentage of fatal crashes involving intoxication, Memphis is last, with a lower rate -- 14 percent -- than even New York City!
This is so curious I'm working on a follow-up post on why Memphis is such an outlier. If you have any thoughts on the matter, please feel free to email me at hgrabar (at) theatlantic.com.
5. Do Southerners drive drunk less?
Nelson also calculated which U.S. cities have the highest and lowest percentages of fatal crashes involving intoxication, regardless of size. Even with no population restrictions, New York and Memphis are on that list, joined by Birmingham and Salt Lake City. Five of the ten are in the South. Remember -- this is not necessarily an endorsement of these cities as places to drive. Memphis has more fatalities per capita than all but two of the largest U.S. cities.
Here's the top ten:
1. Birmingham, Alabama (13.6 percent)
2. Coral Springs, Florida (13.7 percent)
3. Memphis, Tennessee (14.7 percent)
4. Miramar, Florida (14.8 percent)
5. Provo, Utah (15.4 percent)
6. New York, New York (16.3 percent)
7. Surprise, Arizona (16.7 percent)
8. Hialeah, Florida (16.7 percent)
9. Salt Lake City, Utah (17.7 percent)
10. Miami Gardens, Florida (18.3 percent)
And the highest, in which fatal crashes involve intoxication more often than not. Three are in Colorado; two in Wisconsin. None are in the South:
1. Stamford, Connecticut (55.8 percent)
2. Flint, Michigan (55.6 percent)
3. Bellevue, Washington (54.6 percent)
4. Santa Maria, California (54.2 percent)
5. Denver, Colorado (54.2 percent)
6. Colorado Springs, Colorado (54.1 percent)
7. Green Bay, Wisconsin (52.6 percent
8. Lakewood, Colorado (52.5 percent)
9. Billings, Montana (52.5 percent)
10. Madison, Wisconsin (52.3 percent)