ROLLING ROADBLOCKS. Although the Law of Demand induces substitutions and conservations, drivers understand trade-offs.

Drivers have known for years that throttling back is a sure way to improve gas mileage, and the Papins are among those who are consciously slowing down to save. Several airlines have adopted the same tactic, adding a few minutes to flights to save millions on fuel.

But most drivers still appear to be winking at posted speed limits because they say their time is worth more than the gas they'd save by slowing down.

Kelley Goodman, an upstate New York therapist, says gas prices haven't yet gone high enough to justify slowing down.

The article goes on to note responses by truckers, some of whom have no incentive to slow down, and some compelled by their employer to do so. One such employer, Schneider National, is resetting the governors on its trucks. The story bundles that development with some special pleading by the truckers' welfare-rights organization.

The trucking industry's largest lobbying group today called for a nationwide 65 mph speed limit, longer trailers and other steps in an effort to cut greenhouse-gas emissions and save billions of gallons of fuel.

Meanwhile, Green Bay-based Schneider National Inc., one of the country's biggest trucking firms, went still further: The company will voluntarily cut the top cruising speed on its 10,600 tractors to 60 mph, President and Chief Executive Officer Chris Lofgren said during a press conference announcing the industry initiative.

Schneider's slowdown - the firm currently caps cruising speeds at 63 mph - will be equivalent to taking more than 7,200 cars off the highways, Lofgren said, and will save 3.75 million gallons of fuel a year.

"We encourage others in the industry to make this commitment with us," Lofgren said.

What intrigues about this proposal is that it's couched in the language of "sustainability", but somewhat differently from the language of, for instance, the University of Delaware's residential reeducation program (of which more next week).

Limiting cars and trucks to 65 mph could conserve more than 11 billion gallons of diesel and gasoline over 10 years, the American Trucking Associations said in announcing its sustainability proposals.

A longer article offers additional details.

The trucking association said its initiative is primarily an environmental effort, but acknowledged that soaring diesel prices - they currently average $4.15 a gallon - would help boost acceptance among the industry.

Likely to draw the most public attention are the call for a national speed limit of 65 mph for all vehicles and the proposal to allow longer or heavier trucks.

Since Congress repealed the national maximum speed limit in 1995, 32 states have set limits at 70 mph or more on some highways, according to the Insurance Institute for Highway Safety. Thirteen western states allow speeds up to 75 mph.

Trucking has been deregulated for nearly thirty years, yet there are still people who think like public utility managers. Because an agreement to restrict output by slowing down trucks has the prisoners' dilemma property of any restraint of trade, one sells the restriction of output as "in the public interest."

In the short term, what Schneider proposes will simply add to the snarl on the interstates. It's annoying enough when an elephant galumphing along at 70 shoulders into the passing lane to go around a triple maintaining 69. Now imagine the same process, but galumphing along at 63. Never mind: the welfare-rights organization has the chutzpah to ask for longer trucks as well, when anything over 28 feet is a menace in a thickly settled area? Perhaps in the quest of insurers for their own corporate welfare comes countervailing power.

But permitting wider use of double and triple trailers and allowing trucks to carry heavier loads is almost certain to spark opposition.

"A truck that's heavier is less safe, and I think there's already a huge mismatch between a heavy truck and a passenger vehicle, even the biggest passenger vehicle," said Anne McCartt, senior vice president for research at the insurance institute.

Perhaps it's time, however, to ask the truckers to raise funds for their own rights-of-way.

To reduce fuel-eating congestion, the federal government should first clear traffic bottlenecks in such metropolitan areas as Chicago, Atlanta, Los Angeles and Phoenix, followed by road building to address capacity problems, the association said.

"In certain areas of the country we need to build new, truck-only corridors," said Tommy Hodges, head of the trucking group's sustainability task force and chairman of Titan Transfer Inc. of Shelbyville, Tenn.

Mr Hodges, may I introduce the controllers of BNSF Railroad and Union Pacific, who seem to be meeting a need for new freight-only corridors without raiding the public purse.