Here's a number that ought to be memorized by every elected official in the state of Maryland: 485. That's how many people died in traffic collisions in 2011 in this state (the most recent year for which such statistics are available from the National Highway Traffic Safety Administration). That's the equivalent of about 10 full motor coaches.

Yet the number that's being discussed these days in the General Assembly is 70. That's how fast, in miles per hour, some believe motorists should be allowed to drive on certain state highways, and under the circumstances, it's more than a little surprising that raising the speed limit is even on the legislative agenda.

The most sweeping proposal would grant the Maryland State Highway Administration the authority to set a 70 mph speed limit instead of the 65 mph, the current maximum allowed under law. Another would specifically raise the limit to 70 mph on Interstate 68 in Western Maryland. And a third would allow the motorists on the Intercounty Connector to drive at 65 mph instead of the current 60 mph (despite its limit having been raised from 55 mph just last year).

Most states allow 70 mph highways, but Maryland does not. And there's a very good reason for why proposals to raise the limit have been beaten back before — they make the roads more dangerous and raise the risk of a fatal collision.

Can five miles per hour really make that much difference? Certainly not in terms of convenience. Even a motorist driving the full length of I-68 would only save a matter of minutes if allowed to drive 7.6 percent faster. It's stretches the imagination to suggest that the region would somehow enjoy some economic benefit from such a modest change.

Unfortunately, however, the higher speed limit can have serious consequences for highway safety. A study by the American Journal of Public Health found that the decision in 1995 to repeal the national speed limit of 65 mph resulted in an estimated 12,545 more deaths on the highways related to higher state speed limits in the decade following the change.

Indeed, speed remains a critical factor in highway fatalities. As much as distracted driving has gotten much deserved attention of late, NHTSA estimates that speeding is a factor in more than 30 percent of crashes. Nationwide, that means speed helped claim 9,944 lives on the nation's roads in 2011.

In Maryland, that translates to 142 of those 485 lives lost. Only alcohol is a more important factor in fatal crashes.

Supporters of the higher speed limit will, of course, offer the usual reduction to absurdity argument that Maryland's roads would be even safer if the maximum speed limit was set at 45 mph or even 30 mph. But that's not on the table, and such silliness ignores the serious real-world behavior of drivers who use a 65 mph limit to justify going 70 or even 75.

Traffic engineers use a general rule that speed limits ought to be set at the so-called 85th percentile — the number at which 85 percent of motorists believe it is safe to drive a particular stretch of road under ideal conditions. In theory, that minimizes large differentials between motorists (someone going 20 mph faster than someone else, for example) that can contribute to accidents.

That the SHA didn't outright oppose the 70-mph speed limit legislation was apparently due to how the state agency would still retain the ability to set speed limits under the 85th percentile rule. But we would argue that Maryland is such a small state that the 70 mph rule offers too little benefit to bother. The evidence that speed kills is too overwhelming to debate one segment of interstate here or there — even in the rural areas.

There are other reasons to be against the higher speed limit, from the cost of the studies and new signs that would be required to the worsened vehicle fuel efficiency that comes with higher speeds (increasing U.S. dependence on foreign oil, incidentally), but safety ought to be the overriding concern for our elected officials. These are not just numbers but people's lives that hang in the balance, and what would we get in return for 70 mph roads? Not nearly enough to take such a risk.


To respond to this editorial, send an email to talkback@baltimoresun.com. Please include your name and contact information.