Traffic deaths and safety: who's really the safest?

William Lucy of the University of Virginia has written extensively on the question of whether outer suburbs are safer than cities or inner suburbs; he argues, based on traffic fatality data, that outer suburbs are certainly less safe than inner suburbs, and maybe even less safe than cities. (1) 

However, Lucy's analysis is not particularly fine-grained: it analyzes data county-by-county, rather than town-by-town. What's wrong with this?  Often, suburban cities within a county are quite diverse: some share the characteristics of inner suburbs (e.g. some public transit) while others look more like exurbs.  So I wondered whether there is any significant 'safety gap" between inner and outer suburbs. 

Thanks to the City Data website (www.city-data.com) this problem is at least partially soluble. The City Data website has traffic fatality data for some individual communities.

So I decided to give the data a try for one metro area I am somewhat familiar with. Rather than trying to analyze every single suburb of a region, I decided to make a case study of one or two metro areas that I am at least somewhat familiar with, and to focus on suburbs that compete with each other for residents of roughly the same social class. 

First, I examined St. Louis and some of its suburbs.  In 2009, the city of St. Louis had 10.9 car crash fatalities per 100,000 people, and 40.3 murders,(2) for a total violent death rate of 51.2 per 100,000.  How do its suburbs compare? 

First I looked at two central-western inner suburbs popular with upper-middle-class professionals: University City and Clayton.   Between 2005 and 2009, University City averaged 3.8 murders and 1.1 car crash fatalities per 100,000, for a total violent death rate of 4.9/100,000. During the same period, Clayton averaged 2.4 murders and 1.2 car deaths per 100,000, for a total violent death rate of 3.6 per 100,000.  Obviously, these suburbs are far safer than the city of St. Louis, whether measured by car crashes or murders.  

How do outer suburbs compare?  Rather than focusing on the outermost exurbs, I wanted to look at places that compete with University City and Clayton for residents: central-western outer suburbs where bus routes begin to thin out, but are still developed upper-middle-class suburbs rather than ruralizing exurbs.  In particular, I focused on Chesterfield, a booming, job-rich suburb far beyond the region's outer beltway (I-270).  During 2005-09, this suburb had 2.6 car crash deaths per 100,000 and 1.3 murders, for a total of 3.9 violent deaths per 100,000- a little safer than University City, a little more dangerous than Clayton.  (I note that some nearby suburbs, such as Manchester, had even fewer fatalities). 

Then I jumped the St. Louis county Line into St. Charles County, and looked at St. Peters, 25 miles from the city of St. Louis.  St. Peters had no murders, but had 6.2 traffic fatalities per 100,000 residents during 2005-09- definitely more than any of the other suburbs listed above.  Nearby St. Charles had 1.3 murders and 5 traffic fatalities per 100,000 people per year during this period, for a violent death rate of 6.3 per 100,000.

St. Charles County as a whole (which is less dense and thus less developed than St. Peters) looks much more dangerous than St. Peters. Although no statistics were available for 2007-09, 2005-06 traffic deaths averaged 11.2 per 100,000- a result consistent with Lucy's analysis.

Then I looked at another metro area, Buffalo,  Here I varied the analysis by focusing on the middle-class eastern suburbs, as opposed to the most affluent suburbs (which, in Buffalo, are northeast of the city).  The city of Buffalo averaged about 20.4 murders and 10 traffic deaths per 100,000/year between 2005 and 2009.  Cheektowaga, a large inner suburb, averaged 0.5 murders and 4 traffic deaths per 100,000, for a total of 4.5 violent deaths per 100,000.  Because the region's transit system mostly ends at Cheektowaga's eastern boundary (Transit Road) I would guess (if my St. Louis findings were typical) that suburbs further east had higher traffic death rates.  In fact this was the case.  Lancaster, the suburb immediately to the east of Cheektowaga, averaged 21.2 traffic fatalities per 100,000/year from 2005-09. and Elma (just south of Lancaster) averaged 14.3 traffic deaths.  Again, inner suburbs were safer than outer suburbs- though here the gap was much greater than in St. Louis.  (But assuming arguendo that Elma and Lancaster had zero murders, they were still safer than Buffalo).

A look at the more affluent northern suburbs showed a similar growth of traffic deaths as one moves further out.  Kenmore, a tiny, walkable mini-suburb, averaged 1.3 violent deaths per 100,000 (all traffic) from 2005 to 2009.  Amherst, which contains some totally car-dependent neighborhoods and a few with adequate bus service, averaged 4.2 violent deaths per 100,000 (1.1 murders, 3.1 traffic). Tonawanda, a similar northern suburb, also had 4 traffic deaths per 100,000 (and zero murders, giving it a roughly identical violent death rate to Amherst). But exurb-like Clarence averaged 9 traffic deaths per 100,000.  

So if St. Louis and Buffalo are any guide, it appears that the impact of traffic deaths (and the overall level of violent death as well) drops dramatically between the city limits and the innermost suburbs, doesn't change much between the first couple of rings of suburbs, and then rises dramatically in the least developed, least transit-friendly, most exurb-like suburbs. 

(1) http://www.minority.unc.edu/sph/minconf/2004/materials/lucy.et.al.pdf 

(2) Lucy emphasizes the number of homicides caused by strangers.  However, these statistics are far less easy to access and so I have not used them.   Moreover, some homicides are of uncertain origin.