Almost every speed limit is too low

By Alex Mayyasi : qz – excerpt

“We all speed, yet months and months usually pass between us seeing a crash,” lieutenant Megge tells us when we call to discuss speed limits. “That tells me that most of us are adequate, safe, reasonable drivers. Speeding and traffic safety have a small correlation.”…

This “nationally recognized method” of setting the speed limit as the 85th percentile speed is essentially traffic engineering 101…

Luckily, there is some logic to the speed people choose other than the need for speed. The speed drivers choose is not based on laws or street signs, but the weather, number of intersections, presence of pedestrians and curves, and all the other information that factors into the principle, as lieutenant Megge puts it, that “no one I know who gets into their car wants to crash.”.

So if drivers disregard speed limits, why bother trying to set the “right” speed limit at all?…
This is important because, as noted in a US Department of Transportation report, “the potential for being involved in an accident is highest when traveling at speed much lower or much higher than the majority of motorists.” If every car sets its cruise control at the same speed, the odds of a fender bender happening is low. But when some cars drive 55 mph and others drive 85 mph, the odds of cars colliding increases dramatically. This is why getting slow drivers to stick to the right lane is so important to roadway safety; we generally focus on joyriders’ ability to cause accidents—and rightly so—but a car driving under the speed limit in the left (passing) lane of a highway is almost as dangerous.

Traffic engineers believe that the 85th percentile speed is the ideal speed limit because it leads to the least variability between driving speeds and therefore safer roads. When the speed limit is correctly set at the 85th percentile speed, the minority of drivers that do conscientiously follow speed limits are no longer driving much slower than the speed of traffic. The choice of the 85th percentile speed is a data-driven conclusion—as noted lieutenant Megge and speed limit resources like the Michigan State Police’s guide—that has been established by the consistent findings of years of traffic studies…

If people and politicians do want to reduce road speeds to improve safety, or make cities more pedestrian friendly, Megge says “there are a lot of other things you can do from an engineering standpoint.” Cities can reduce the number of lanes, change the parking situation, create wider bike paths, and so on. It’s more expensive, but unlike changing the number on a sign, it’s effective…

In its 1992 report, the US Department of Transportation cautioned, “Arbitrary, unrealistic, and nonuniform speed limits have created a socially acceptable disregard for speed limits.” Lieutenant Megge has worked on roads with a compliance rate of nearly 0%, and a common complaint among those given traffic citations is that they were speeding no more than anyone else. With higher speed limits, Megge says, police officers could focus their resources on what really matters: drunk drivers, people who don’t wear seat belts, drivers who run red lights, and, most importantly, the smaller number of drivers who actually speed at an unreasonable rate.

It seems counterintuitive, but it’s a formula Americans should love: Raise speed limits, make roads safer…

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