CMU’s TrafficSTATS

Carnegie Mellon University’s Center for the Study & Improvement of Regulation recently introduced TrafficSTATS (STAtistics on Travel Safety), a Web tool for analyzing traffic-fatality data. It is based on two U.S. government databases, one that tracks all accidents that involved a fatality, and another that estimates the total amount of driving done in the U.S. by various characteristics such as region, vehicle type, and such. The time range covered was 1999 to 2004.

I took a quick look, and here’s what caught my eye:

• Accidents with fatalities were extremely rare—much rarer than I would have guessed—in terms of the amount of driving done. On average, an accident with a fatality occurred once in 100 million “person miles.” (A person mile counts one mile for each person that traveled that mile; if a car with three passengers travels one mile, that’s three person miles.) A fatality could be anyone involved, including nonmotorists.
• That said, if you multiplied the number of people in the United States by the number of person miles they traveled, the result was on the order of 40,000 traffic fatalities per year.
• A motorcycle was 30 times as likely to be in a fatal accident than the average personal vehicle. (That’s in terms of person-miles traveled, so the metric is something like the risk per mile traveled.)
• Females were less than half as likely as males to be in a fatal accident.
• The average weekend day had 35% more fatal accidents than the average weekday (although Friday was a well-above-average weekday, enough to look more like Saturday and Sunday than its weekday peers).
• In terms of person miles, people in the “East South Central” region (Alabama, Kentucky, Mississippi, Tennessee) were more than twice as likely to be in a fatal accident as people in the “New England” region (Connecticut, Massachusetts, Maine, New Hampshire, Rhode Island, Vermont). Those were the two regional extremes.
• In terms of person miles, age groups 16-20 and 75-84 were each more than twice as likely as average to be in a fatal accident. 21-24 was slightly less than twice the average. Between 25 and 64, everything was under the average.

There are hints of messiness in the underlying data, but for simple analyses like the above, it’s probably not a big deal. For those that want to work with the raw data sets, they are available.