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Why speed limits are rising

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CarInsurance.com

Speeding

Watch out for the old guy in the hat doing 50 mph in the left lane, because he's the threat, not you.

At least that's the sentiment that appears to be gaining ground as states begin raising -- that's right, raising -- the speed limit on some highways.

The thinking goes like this: If most drivers are doing 80 mph anyway, why discourage the others from joining the flow of traffic, particularly given the number of flagrantly bad lane-changers out there?

Predictably, motorists are cheering and the auto insurance industry and safety experts are warning of increased hazards.

Go ahead, step on it

Kansas raised the speed limit on more than 1,000 miles of divided four-lane highways to 75 mph effective July 1. Louisiana reset portions of a rural interstate to 75 mph in April, after observing that 85 percent of drivers were going at or below that speed. The same month, Ohio upped the speed on its turnpike to 70 mph.

Late last year, Virginia raised the speed limit on its rural interstates to 70 mph. And the Texas House of Representatives recently passed legislation to boost limits to 85 mph on highways in west Texas.

If the Texas Senate goes along, these will be the first U.S. highways to break the 80 mph barrier (Texas and Utah have each tried 80 mph limits) since President Richard Nixon enacted a national speed limit of 55 mph in response to the 1973 oil crisis. The national limit was raised to 65 mph in 1987 and authority to set highway speeds reverted back to the states in 1995. Speeds have been rising slowly and sporadically ever since.

But it's hardly open season on the open road. Speed limits are rising where the highways are emptiest, and the consequences of a traffic ticket on your car insurance premiums aren't going to shrink.

Go with the flow

It's about time for higher limits, say proponents. For years, state transportation departments have set speed limits based, in part, on how fast traffic already moves. Rural multilane highways where motorists typically exceed the posted limits should do the same, say proponents of higher limits, as long as traffic engineering studies deem each increase to be safe.

"What you want is free-flowing traffic, where's there's no encumbrances to the traffic," says Gary Biller, executive director of the National Motorists Association. "So you're seeing traffic in its natural state."

Studies by the Michigan State Police have found that the safest speed limits are those that capture the most drivers. Less passing (and presumably less finger-waving) equals fewer incidents. The terms of this theory are these:

  • Prevailing speed: The speed at which most drivers feel comfortable traveling on a set stretch of road, regardless of the speed limit. In experiments by the Michigan researchers, prevailing speed did not appreciably change even when the posted speed limit did. In one case where the limit was raised from 55 mph to 70 mph, the prevailing speed actually dropped from 73 mph to 72 mph.

  • The 85th percentile: The speed that captures 85 percent of drivers, meaning that the bulk of drivers are going at or below this speed, regardless of the posted limit. The Michigan State Police has pegged this as the optimum target in order to reduce speed variance.

  • Lowest speed variance: The sweet spot where the difference between the fastest and slowest drivers is smallest. Studies show that the number of crashes drop as speed levels even out.

Not so fast

Citing contradictory speed studies, not all state lawmakers are ready to raise speed limits, however.

"The body of evidence clearly points to the connection between higher speed and deaths," says Russ Rader, a spokesman for the Insurance Institute of Highway Safety (IIHS). "I've heard the opponents say, 'We've had higher speeds and yet we've had the lowest death rates in the last few years.' But in recent years that's entirely due to more crash-worthy cars.

"You have to go to the areas where the speed limits have changed," Rader says. "When you look at the specific rural interstates where the speed limits have been raised, there are more deaths on those roads."

A 2009 study in the American Journal of Public Health looked at specific roadways, attributing 12,545 deaths between 1995 and 2005 to increased speed limits.

Here are the consequences of faster driving that safety experts want you to keep in mind:

  • Longer stopping distances: Exact calculations of braking time and distance vary depending on a multitude of factors, but it's hard to deny basic physics: The faster you're going, the longer it's going to take to stop.

  • Less time to respond. If it takes one second to recognize an emergency, and another second to take action, in those two seconds a car going 85 mph will have traveled 249 feet before the driver reacts, . or about 16 car lengths. At 65 mph the distance drops to 190 feet.

  • Speed kills. Accidents at high rates of speed aren't just worse; they're much worse, and they're more likely to be fatal.

To see speed limits by state, go here.

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