Fact-Checking the Toyota Hearing: Lower Speeds Increase Safety

Megan McArdle at the Atlantic, writing on today’s Toyota hearing in the House oversight committee, hears Transportation Secretary Ray LaHood claim that “lowering the speed limit to 30 mph would not save any lives, which is why we have minimum speeds on highways.”

LaHood, at left, with the president at right. (Photo: whitehouse via Flickr)

Leaving aside the gaping logical hole in that statement — which Robert Mackey of the New York Times suggests (check out the 12:04 post here) may have come from Souder’s argument that lower speed limits would save more lives than “100% safe” cars — there is plenty of research out there pointing to the beneficial effects of lower speeds on safety.

Traffic author Tom Vanderbilt recently cited the impact of 20 mile-per-hour urban speed zones on reducing road injuries in the United Kingdom, and a 2007 study by the AAA Foundation for Traffic Safety [PDF] outlined the following “general rule of thumb”:

When travel speed increases by 1%, the injury crash rate increases by about 2%, the serious injury crash rate increases by about 3%, and the fatal crash rate increases by about 4%. The same relation holds in reverse: a 1% decrease in travel speed reduces injury crashes by about 2%, serious injury crashes by about 3%, and fatal crashes by about 4%.

Could LaHood be unaware of the relationship between lower speeds and decreased risk of injury? It’s certainly possible — despite the former GOP lawmaker’s good record on infrastructure reform and sustainability, both in concept and in practice, he remains a relative newcomer to the nitty-gritty of transportation, as the Times reminded readers in a highly readable profile last year.