As you zip down the highway at 70 mph, remember that your lead foot will cost you at the pump in these days of $4-a-gallon gas.

Some lawmakers in Congress have certainly considered the consequences of your driving habits. And they want you to slow down.

Record-high gas prices have triggered talk that it may be time to lower the speed limit on federal highways to 55 or 60 mph.

"I think that's a great way to save fuel," said U.S. Rep. Heath Shuler, D-Waynesville, N.C. "I think it would be the right thing to do."

U.S. Sen. John Warner, R-Va., raised the possibility of reducing the speed limit to 55 or 60 mph early last month. He asked Energy Secretary Samuel W. Bodman to study whether a lower speed limit would reduce gas prices at the pump and report back on how much fuel it would save.

In the House, U.S. Rep. Jackie Speier, D-Calif., has filed legislation that would impose a national speed limit of 60 mph on highways in urban centers and 65 mph in less populated areas. A hearing on the bill hasn't yet been set.

The push for a lower speed limit harkens back to 1974, when the country was facing another energy crisis and Congress and President Richard Nixon reduced the limit to 55 mph in response to the Arab oil embargo.

Congress eased up a bit in 1987 and allowed states to raise the limit on rural highways to 65 mph. Eight years later, Congress repealed the law altogether, leaving states free to set their own speed limits.

Today, 32 states have raised speed limits to 70 mph or higher on some portion of their roadways.

A report by the Congressional Research Service concluded that the 55 mph speed limit enacted in 1974 resulted in reduced consumption of 167,000 barrels of petroleum a day, roughly a 2 percent reduction in the nation's highway fuel consumption.

"Given the significant increase in the number of vehicles on America's highway system from 1974 to 2008, one could assume that the amount of fuel that could be conserved today is far greater," Warner wrote to Bodman in a letter dated July 3.

Other supporters say lowering the speed limit would not only save fuel, it also would save lives.

"You can argue whether 65 is the number or 55 is the number," said Judie Stone, president of Advocates for Highway and Auto Safety, a coalition of consumer groups and insurance companies. "But the faster you go, the more dangerous it is. And it's exponential. Your chances of being involved in a fatal crash go way up once you get in those upper ranges."

Opponents counter that lowering the speed limit is pointless because most drivers will simply refuse to go that slow and many states barely enforced the 55 mph speed limit when it was in effect.

"No other law, other than Prohibition, has not been adhered to as much as that 55 mph limit," said Bonnie Sesolak of the National Motorists Association in Wisconsin. "It just wasn't the answer then, and it's not the answer now."

Even critics concede that lowering the speed limit would save fuel.

While each vehicle reaches its optimal fuel economy at a different speed or a range of speeds, gas mileage usually decreases rapidly at speeds above 60 mph, according to the Department of Energy's web site www.fueleconomy.gov.

Every 5 mph slower you drive on the highway can lead to 7 percent or 8 percent in fuel savings, David L. Greene, a transportation official at Oak Ridge National Laboratory, told a congressional panel last month.

E-mail Michael Collins at collinsm(at)shns.com

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