You've seen the bumper sticker asking, How's my driving? ¶ For truckers, the answer has been, "Slower."

Trying to blunt the effects of high fuel prices, truckers have tucked themselves into the right lane, where they're saving fuel and touting the benefits of slower speeds on the environment and highway safety. And they're asking others to do the same, calling for reduced speed limits nationally. But many believe the $4-per-gallon price still isn't high enough to make Americans ease up on their gas pedals.

The American Trucking Association has called for Congress to set the highway speed limit at 65 miles per hour nationally -- 5 mph below what's now allowed on Minnesota interstate highways outside the metro area. But a mandated speed-limit rollback will be a tough sell, only 13 years after the widely flouted national 55-miles-per-hour standard was lifted.

The American Automobile Association opposes lower speed limits. Gail Weinholzer, spokeswoman for AAA Minnesota/Iowa, said drivers tend to find their own safe speed limits based on traffic and road conditions.

"If you try to enforce a speed limit that seems unreasonable to a majority of drivers, they tend to exceed it anyway," Weinholzer said.

St. Cloud trucking firm owner Greg Langford thinks a rollback would be wise.

"Some people just don't get it. And it's too bad," he said.

"Because people should understand that by driving a little slower, you're getting that better fuel economy," said Langford, a member of the Minnesota Climate Change Advisory Group who has dialed down his fleet's speed limit from 72 mph to 63 over the past three years. "If we're going to reduce our dependence on foreign oil, we've got to consume less. Which we're doing."

The connection between slower highway speeds and better gas mileage has been widely understood since the fuel shortages of the 1970s, which led to the institution of the national 55 mph limit in 1974. But advocates for a speed limit rollback say there are new urgencies.

One is that the goal of U.S. energy independence is even more remote today than it was 30 years ago. U.S. Sen. John Warner, R-Va., who called in July for a study of lower speed limits, noted that the United States now imports 60 percent of its oil, double what it did in 1974. He said the 55 mph limit saved the nation 167,000 barrels of oil per day, and would "save" far more today, because there are nearly twice as many cars on U.S. roads. Daily U.S. oil consumption today is 20.7 million barrels, according to the Energy Information Administration.

Rising greenhouse gas emissions are also now getting more attention. Reducing miles per gallon (and driving, period) is one of the key strategies in reducing the output of carbon dioxide, one of the major causes of global warming. Transportation accounts for 25 percent of Minnesota's greenhouse gas emissions.

A single semitrailer truck that cut its average speed from 70 mph to 65 mph could reduce its CO2 emissions by 10 tons, or 7 percent a year, according to the U.S. Environmental Protection Agency. That's equivalent to removing almost two cars from the road.

Links between crashes and speed limits are unclear. Truckers insist that what is more dangerous than high speed limits is wide differences in speed limits between cars and trucks -- now 15 mph in some states. "I think we get a triple win if we do this," said John Hausladen, president of the Minnesota Trucking Association who served on a task force of the national truckers' group that is advocating the 65 mph limit. "We reduce fuel consumption, we save lives and we reduce CO2 emissions."

Penciling it out

James Mitchell, a trucker from Raleigh, N.C., who was gassing up at a truck stop in suburban Rogers on Wednesday, said he slowed in April from 68 mph to 60, and boosted his diesel miles-per-gallon from 6.2 to 7.9, a 27 percent increase.

"I can't afford to drive that fast," he said of his former speeds.

Jason McIntire, a trucker from Fairfield, Iowa, said that scaling back from 70 mph to 62 mph might mean spending $10,000 less a year to run his truck. The obvious question is whether all the people not getting paid to drive by the hour or by the load might be willing to slow down, to save fuel, or to cut down on CO2 emissions, or just to savor the scenery. Or because it might be the law.

Unlikely, said David Levinson, a professor of civil engineering and a researcher at the University of Minnesota's Center for Transportation Studies. That's because the cash savings don't match the loss of time, perceived or real.

Consider a 235-mile road trip. According to the EPA, an auto driver would use 8.8 gallons of gas at 70 miles per hour, and 7.3 gallons at 55 mph. If he or she paid $4 per gallon for gas, the cash savings would be $6. But the trip would take almost an hour longer. And most people value their personal time at about $13 an hour, according to government calculations.

So the time "lost" would have a higher value than the fuel saved, undermining a major reason to ease off the gas pedal. That's been the case in Europe, Levinson pointed out, where both gas prices and speeds are much higher than in the United States. In the future, a carbon tax, which would put a cost on carbon dioxide emissions from a range of activities, could have a slow-down effect.

In any case, there doesn't seem to be much support for reduced speed limits by the people who can make it happen. Sen. Norm Coleman, R-Minn., while advocating reduced oil consumption, wouldn't put a high priority on reduced speed limits, said spokesman Leroy Coleman. His DFL opponent, Al Franken, opposes reduced speed limits while favoring tougher fuel-efficiency standards and development of renewable energy sources, said spokeswoman Jess MacIntosh. Sen. Amy Klobuchar, D-Minn., has indicated she would prefer to educate drivers on savings so they would slow down voluntarily.

Bill McAuliffe • 612-673-7646