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Higher speed limit will mean lost lives

Last modified: 1/9/2012 12:00:00 AM
Increasing the speed limit on New Hampshire interstate highways is not the worst idea to come before the Legislature, nor would it be the most dangerous change in public policy that the lawmakers elected in 2010 have embraced. It is, nonetheless, a very bad idea, one that would decrease safety, increase insurance costs, deplete a finite resource faster, and do needless harm to the environment.

The fundamental logic behind the move to increase the limit, championed by Republicans Steve Vaillancourt of Manchester and Paul Mirski of Enfield, is badly flawed. They claim that many motorists exceed the state's 65 mph speed limit and break the law with impunity on a daily basis - and they're right. But raising the speed limit to 70 won't solve that problem. Some motorists will continue to cruise along at 70 or 72 mph - a state police spokesman once admitted that troopers rarely stop someone unless they're going more than 7 miles per hour over the speed limit - but many will instead drive at 75 mph or more. Horrifyingly, some of them will be talking on a cell phone.

Speed limits, as New Hampshire's drivers' manual states, "are the maximum speed you may travel under ideal conditions." A speed safe in one weather condition courts disaster in another. A speed that's safe for an alert experienced driver could be fatally irresponsible for an inexperienced driver, let alone one who's tired or distracted. A speed that's safe on Interstate 93 in Thornton would likely be hazardous in Salem. The higher the speed, the less time a driver has to respond to a potentially dangerous situation. At 65 miles per hour a motorist with average reaction time driving a vehicle with average performance and good tires can expect to stop 345 feet after perceiving danger. At 70 mph that distance increases to 388 feet. At 75 the distance becomes 433 feet. Raise the speed limit, and the risk of an accident goes up.

The state of Iowa increased the speed limit on its rural interstates to 70 mph in 2005. The number of drivers exceeding the speed limit by 10 mph decreased by more than 50 percent, but the number of serious crashes increased by about one-third and the number of serious cross-median crashes increased by 80 percent.

In 1974, in response to an oil embargo by Arab nations, the federal government reduced the speed limit on interstates to 55 mph. The change saved 4,000 lives annually, according to the National Research Council. Were the lives saved, reduced oil consumption and damage to human health and the environment worth the sacrifice in time that came with a 55 mph limit? We don't know. Nor would we support a return to 55 now, in a society that lives life at hyperspeed. But 65 mph is a reasonable compromise.

Every vehicle has a different optimal speed for fuel economy, typically between 35 and 50 mph. Past that speed fuel consumption increases by between 5 and 10 percent for every additional 5 miles per hour, according to the U.S. Department of Energy. More gas burned equals more pollution. Increasing the speed limit would increase auto emissions and speed global warming.

New Hampshire can't afford the additional cost in lost or damaged lives and damage to the environment that would result from a higher speed limit. The bill imposing one should flunk inspection and be taken off the road.


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