Compact Cities Have Fewer Car Deaths

When traffic engineers widen roads and build new roads, they often cite "safety" as an argument.  Under this theory, the widest, straightest, fastest roads are the safest.  If this were true, car-oriented cities dominated by such roads would be safer than more compact, transit-oriented cities.  Right?  Wrong.

I tested the theory by going to city-data.com and examining traffic fatality rates for two groups of large cities: large cities where over 20 percent of workers use public transit (Philadelphia, San Francisco, Chicago, and Boston- for some reason the website lacked data for New York and Washington) and for the largest cities where under 10 percent of workers use public transit (Houston, Phoenix, San Antonio, San Diego and Dallas).

The four "transit cities" consistently had lower fatality rates than state and national averages: Boston (the safest) had only 3.8 traffic deaths per 100,000 per year between 2005 and 2009.  San Francisco (at 5.0), Chicago (at 6.3) and Philadelphia (at 6.6) were slightly less safe.

The largest "car cities" did not do so well: the safest, San Diego, had 7.1 fatalites per 100,000 people in the average late 2000s year, slightly more than any of the transit cities.  The others were significantly worse: San Antonio averaged 9.4 traffic fatalities per 100,000, Houston 9.8, Dallas 10.8, and Phoenix 12.3.  

One might think that the car cities are more dangerous for pedestrians but not for motorists and their passengers.  But even when pedestrian fatalities are excluded, the car cities do worse.  The compact cities' non-pedestrian fatality rates ranged from 2.4 per 100,000 per year (Boston) to 3.9 (Chicago and Philadelphia). The car cities' non-pedestrian fatality rates ranged from 5 (San Diego) to 8.2 (Phoenix).  Even the most dangerous compact city was safer for non-pedestrians than the safest of the larger car cities.  I suspect that this is probably due to road design: in car cities, streets are more likely to be designed for higher speeds, which means that crashes are more likely to be fatal.

It seems to be pretty well settled that car cities are more dangerous for pedestrians; but when driver fatalities are included, such cities are on balance more dangerous for everyone.