Reporting on pedestrian life in the D.C. area

How a car's speed affects the chances a struck pedestrian survives

May 11, 2012 - 01:39 PM
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(Photo: flickr/wwwShootJoecom)

How likely are you to survive if a car strikes you at 20 miles/hour? 30 miles/hour? 40?

The Chicago Department of Transportation, led by former DDOT director Gabe Klein, includes the following chilling and instructive chart in its new transportation priorities report, a reminder of what many already know but helpful to see again. Chicago is pushing to lower its residential speed limits from 30 miles/hour to 20 in the name of reducing traffic fatalities — the city hopes to lower the number to zero within a decade. Last year D.C. Councilmember Muriel Bowser suggested that D.C. lower its residential speed limits from 25 miles/hour to 15 but that never passed into law.

Chocolate strawberries
(Photo: CDOT)

Note: I've seen the exact percentages vary over the years depending on what sources you look at. Consider this stat from New York City's transportation department last year: "If a pedestrian is hit by a car traveling 40 m.p.h. or faster, there's a 70 percent chance that pedestrian will be killed; at 30 m.p.h., there's an 80 percent chance that the pedestrian will live." The same principle applies, but the chances differ considerably. In 1999, the National Highway Traffic Safety Administration pointed to a classic collection of studies from the early '90s that together suggested "5 percent of pedestrians would die when struck by a vehicle traveling 20 mph, about 40 percent for vehicles traveling 30 mph, about 80 percent for vehicles traveling 40 mph, and nearly 100 percent for speeds over 50 mph." These numbers come close to what Chicago just released. These exact Chicago numbers appear to come from the U.K. Department of Transportation's 1987 analysis, entitled Killing Speed and Saving Lives and cited frequently enough by the federal government and pedestrian safety advocates ever since.

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