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U.S. traffic death increase caused by speeding, says new study

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“You can’t tackle our rising epidemic of roadway deaths without tackling speeding.”

Your chances of surviving a crash that happens at 25 mph are very good, which is why many cities want to lower their speed limits.
Andrey Bayda/Shutterstock

Traffic deaths have been on the rise in the U.S. for the last few years and experts can’t agree why. Some say it’s due to an overall increase in driving, while others have tried to blame smartphone-holding pedestrians. A new study out from the National Transportation Safety Board declares there’s a singular and unequivocal reason for the uptick in deaths: Speed is what’s killing Americans.

“You can’t tackle our rising epidemic of roadway deaths without tackling speeding. Speed kills,” said NTSB acting chairman Robert L. Sumwalt. “This study examines how it kills and what actions can be taken to save lives and prevent speeding-related crashes.”

The study looked at U.S. passenger vehicle crashes from 2005 to 2014 and found that speeding was the main factor in 112,580 deaths, or about 31 percent of all traffic fatalities. That figure is made more shocking when you look at the number of people killed in crashes where alcohol was the main factor. During that same period, almost the exact number of people—112,948—were killed by drunk drivers. (This data doesn’t even include the uptick in overall traffic deaths that’s occurred over the past two years.)

Drunk driving and speeding have a lot in common, as the NTSB’s report highlights. Like someone driving under the influence, a driver who is speeding increases both the likelihood of being in a crash and also the likelihood that someone in or near that person’s car will be killed or seriously injured.

That’s why one of the major recommendations from the NTSB is to change the consequences for speeding to match that of a DUI. Driving under the influence carries much heavier penalties than speeding, for example, with many states automatically suspending a license if drivers blow over a certain blood-alcohol level. National campaigns have also successfully created a cultural stigma around driving drunk, yet a similar approach has not been taken to raise awareness about the dangers of speeding.

“People don’t think of speeding the way that they think about some other hazardous driving behaviors,” said Sumwalt at the NTSB board meeting this week. “Unlike other crash factors such as alcohol impairment or unbelted occupants, speeding has few negative social consequences associated with it, and does not have a leader campaigning to increase public awareness about the issue at the national level.”

Recommendations also include expanding enforcement tools like speed cameras, which, as Stephen Miller notes at Streetsblog, are proven to work but are illegal in many states. Enforcement is important because going just ten miles over the speed limit can make the difference between life and death. In a crash, the severity of injuries increases dramatically depending on the speed of a driver—a pedestrian hit at 30 mph has a 60 percent chance of survival, while someone hit at 40 mph only has a 40 percent chance of living.

Another problem the NTSB report cites is with the speed limits themselves, which aren't actually set to prevent crashes—they’re based on an archaic formula calculated around driver behavior. Back when highways were first built, traffic engineers observed the speed of drivers on the mostly rural roads and set limits meant to encompass a speed the majority of the cars were going—about 85 percent, which is why this practice is called the “85 percentile rule.”

The 85th percentile rule has been adopted as policy in most states, and has been extrapolated to define standards for acceptable speeds on a wide variety of roads. But as the NTSB report admitted, this policy doesn’t make any sense when it comes to saving lives, and needs to be revisited:

In general, there is not strong evidence that the 85th percentile speed within a given traffic flow equates to the speed with the lowest crash involvement rate. Alternative approaches and expert systems for setting speed limits are available, which incorporate factors such as crash history and the presence of vulnerable road users such as pedestrians.

This federal assessment comes at a critical time for U.S. cities, many of which have joined the international Vision Zero movement to eliminate traffic deaths. In fact, the Vision Zero methodology for making safety improvements—using crash data and assessing the vulnerability of pedestrians and cyclists to redesign streets—is very similar to the NTSB’s recommendations.

A road diet proposed for Atlanta’s Midtown neighborhood is meant to make the street safer for people walking and riding bikes
Midtown Alliance

But even though cities are pledging to make streets safer, these changes are becoming difficult to implement at the neighborhood level as drivers complain that new road configurations which slow traffic or offer car-free travel alternatives—often called road diets—are extending their commute times. In Los Angeles, a beachside community filed a lawsuit against a road diet (which was later reversed), and another councilmember is trying to ban road diets—even though these redesigned streets have been proven to save lives.

There are some cities that are succeeding in getting drivers to slow down. Boston recently reduced its speed limit to 25 mph citywide and announced a “Slow Streets” program that will redesign streets in five communities to help keep drivers at 20 mph or below.

The changes will include traffic calming devices like curb bump-outs and speed humps, safety infrastructure like crosswalks and bike lanes, and also “visible cues” for drivers to slow down. The city is promoting the program as a way to improve quality of life across a whole range of metrics, from a reduction in emissions to economic development. But hopefully Boston can convince residents that the best “quality of life” metric for slow streets is actually saving lives.