When you think about it, it’s kind of messed up that on any given day, a small mistake behind the wheel could easily lead to someone getting injured or dying. But some cities, like Seattle, are experimenting with a way to make those mistakes less frequent and less severe.
According to new research from the Insurance Institute for Highway Safety (IIHS), we now have good evidence to back up the assumption that lowering speed limits saves lives. The group studied a recent measure implemented by Seattle, Washington, to lower speed limits throughout the city.
In 2016, the local government decided to lower the default speed limit on arterial roads from 30 to 25 mph (48 to 40 km/h), and on smaller roads, the limit was lowered from 25 to 20 mph (40 to 32 km/h).
The theory was that, since traveling at higher speeds gives drivers less time to react to unexpected events, and increases the amount of energy in a crash, lowering the speed limits would help in two ways. And it did!
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In the downtown core, where the speed limit change was most widely publicized and implemented, the odds of an injury crash reduced by 17 percent. Looking at arterial roads alone (the slightly higher speed ones), the risk of injury accidents fell by 20 percent.
The IIHS says that these are statistically significant reductions in rates of injuries relating to accidents. More impressively, the change came at a time when three other cities in Washington (whose accident rates served as control data) saw the rate of injuries rise.
“These results suggest that communities can reap substantial benefits by lowering speed limits,” said IIHS Senior Research Transportation Engineer Wen Hu, the lead author of the study. “To reduce injuries even further, communities should combine lower speed limits with engineering solutions, public education about the importance of reduced speeds, and high-visibility enforcement.”
However, the results were the most pronounced in the city center. Although injury rates fell in other parts of the city, too, they were not by statistically significant numbers. That doesn’t mean that these results aren’t important, though.
“Everybody thinks of highways when we talk about speed limits, but reducing speeds on city thoroughfares and residential streets is just as important,” David Harkey, IIHS President, said. “Nationwide, nearly a third of crash deaths occurred on urban arterials in 2020.”
