Phoenix was reputed to be America’s 7th safest city, according to this survey which looked at three factors relating to insurance. Clearly the stuff of newspaper-filler stories. Intrigued, I see that the survey involves ranking cities in three categories 1) Crime, 2) Natural disasters, and 3) Traffic safety; though it wasn’t clear how they were weighted. For example, traffic fatalities claim far more lives than murder, and the number of deaths in the U.S. due to natural disaster is miniscule.
That being as it may, their source for traffic safety rankings is the “Allstate America’s Best Drivers Report” (tm!), which Allstate claims “Reveals Safest Driving Cities”.
What it actually measures is the statistical likihood of having an auto insurance claim. Which Allstate claims, and I think sounds reasonable, as a proxy for the number of MV collisions. The next leap, which is demonstrably false, is that fewer collisions translates into “safety”. One glaring data point is enough to disprove this: cities of similar size are frequently and for good reasons ranked against one another; it just so happens that Phoenix and Philadelphia have virtually the same population, and are currently the 5th and 6th largest city in the U.S. Actual fatality data reveal that Phoenix is significantly more dangerous than Philadelphia, yet Allstate’s proxy data says just the opposite:
|NHTSA Fatality Data||Allstate data|
|City||Killed||population||killed per 100K||time between collisions||rank (higher=worse)|
|Philadelphia||95||1547297||6.14||60.2% worse||6.2 years||187|
|Seattle, WA||30||616,627||4.87||25% worse||8.0 years||147|
|Phoenix AZ||159||1593659||9.98||1.1% better||10.1 years||74|
Source: NHTSA Traffic Safety Facts 2009 (latest year available), Table 124 811402.pdf, and Allstate (follow link above; current year result they refer to as 2011, is similar to 2005-2010 ). Notes: overall U.S. fatals/population/ratePer100K = 33,808/307,007,000/11.01
So, Allstate’s data merely shows that Phoenicians suffer from fewer fender-benders than Philadelphians; but say nothing about safety.
Why is Phoenix so dangerous? The main reason is probably because it’s “Dangerous by design”, with a higher priority on moving more cars, at higher speeds; and a lower priority on getting everyone to their destinations without being killed. More driving could explain some but not all of the gap; this, in itself, a symptom of poor land-use choices.
I threw Seattle into the table simply because of this recent op-ed that aggravated me: why-seattle-is-safer-than-phoenix. Phoenix and Seattle are quite dissimilar in population, but here again the Allstate data claims Seattle is significantly more dangerous than Phoenix when just the opposite that’s true.
By the way
I always have trouble finding this page at www-nrd.nhtsa.dot.gov (which can be found by searching for FARS, then clicking on “publications”) where it lists publications like Traffic Safety Facts; e.g. 2009 Traffic Safety Facts Data Summary Booklet ; and 2009 Traffic Safety Facts FARS/GES Annual Report, they list back to about earlier 1990’s.