The government is considering a proposal to force big-truck drivers to put front brakes on their rigs.

Nearly 30 percent of the nation's 500,000 long-haul drivers are rolling over the nation's highways with only their rear brakes to stop them in an emergency. And they're doing it legally, under a federal rule dating back to 1952.

The rule originally was intended to help truck drivers avoid front-wheel lockup and maintain control of their vehicles in panic stops.

But safety advocates, as well as some truckers' groups, long have argued that the rule is at best out of date and at worst an invitation to highway mayhem.

Big trucks, weighing up to 80,000 pounds fully loaded, already have stopping distances that are twice as long as those of most cars, the critics say. Allowing the big rigs to run without front brakes increases their stopping distances by as much as 66 percent.

A fully loaded tractor-trailer traveling 60 mph on dry concrete pavement requires 250 to 300 feet to stop with all brakes working, according to government tests. Without the front brakes, the stopping distance can increase by as much as 139 feet, the tests show.

All rigs built since 1980 have been required to have front brakes when they leave the factory. But many drivers and trucking companies, who believe they are safer without the brakes, remove or disable them.

Now, after months of examining new studies on tractor-trailer braking and looking at advances in braking technology, Federal Highway Administration officials say that the critics might be right.

The 1952 rule, originally implemented by the Interstate Commerce Commission and now on the books of the FHA, "clearly was based on studies and engineering done at that time," said Richard P. Landis, the FHA's administrator for motor carriers.

"The thinking then was that steerability was more important than the ability to brake. The thinking was probably sound at that time. But since then, there have been more studies," most of which indicate that the 1952 rule should be scrapped, Landis said.

Changing or eliminating the 1952 rule not only would improve highway safety, but it also would put the government in agreement with itself, according to safety advocates and Transportation Secretary Elizabeth Hanford Dole.

While the FHA allows trucks to operate without front brakes, the National Highway Traffic Safety Administration, which oversees vehicle design and construction, requires manufacturers to install front brakes on all new rigs.

"A simple and immediate way to begin solving truck safety problems is to require that all trucks have operable front brakes. But unfortunately, two offices in the same federal department are contradicting each other on this," the Washington-based Insurance Institute for Highway Safety said last month in petitioning the FHA to reconcile its differences with NHTSA.

Dole, who has jurisdiction over the NHTSA and the FHA, said reconciliation is desirable. "We are drafting a notice of proposed rulemaking, which would eliminate the 1952 provision in the . . . regulations and make it consistent with what NHTSA is doing," she said in recent testimony before the House appropriations subcommittee on transportation.

Rulemakings are lengthy undertakings, often prolonged by legal and political warfare. But the betting in the trucking industry -- among manufacturers, carriers and drivers -- is that the government won't run into many roadblocks in this case.

"We have no objection to requiring the use of front brakes on trucks," said Mike Parkhurst, editor and publisher of "Overdrive," a major editorial voice for the nation's 150,000 independent truckers. "We think that it is better to have that extra braking power," Parkhurst said.

"Overdrive" surveys show that about 30 percent of the country's 500,000 long-haul drivers, independents and company employes, operate their big rigs with "backed-off," or disconnected, front brakes, Parkhurst said.

Backing-off the brakes usually means that the driver has adjusted the valve on the air-brake chambers to allow so much air to escape that the brakes become useless, Parkhurst said. Disconnection can involve a variety of methods, including plugging the passageway between the air hose and the brake chamber with a coin.

Twenty years ago, because of the relatively primitive state of heavy-truck brakes, drivers felt that it was safer to decouple front brakes to avoid front-wheel lock on slippery surfaces during panic stops, Parkhurst said.

"They really were afraid that they would lock up and jackknife," flipping over the entire rig, Parkhurst said.

"A lot of drivers still have that psychological fear today," even though it is groundless because of technological advances such as air-brake limiting devices, improved engine braking, powerful disc brakes and computer-monitored braking, Parkhurst said.

"We want to get the safest arrangement of driver and truck that we possibly can," said Thomas J. Donohue, president of the 3,000-member American Trucking Associations.

ATA has been trying to combat growing public criticism of its membership with a $1.5 million print and media advertising campaign, including a television spot that has been running exclusively in the Washington area.

The theme of the campaign, "Safety Is Our Driving Concern," is more than a public-relations gimmick, Donohue said. It means that "we're willing to support whatever the government does in truck safety as long as they're willing to consult with the real experts," the people who make and drive the trucks, he said.