"Such legislation would be an effective step in addressing the threats we now know await," Acklie said in his testimony. "The possibility of a truck being used as a weapon of mass destruction, while unthinkable before, is now a reality."

No one at the hearing articulated a credible threat to use the $600 billion trucking industry in such a way.

But testimony from lawmakers and other witnesses centered on the alarming vulnerabilities of that business, which have been magnified since the air attacks on New York and Washington.

Examples were raised about shortcomings in the driver permitting system, including the recent indictments or arrests of people who allegedly sold or obtained fraudulent commercial driver's licenses in Pennsylvania and Illinois.

Unease also was apparent when witnesses described the daunting task of trying to account for a gigantic industry comprised of huge corporate fleets, smaller companies and independent operators spread across the country.

MORE THAN 10 MILLION TRUCK DRIVERS

There are more than 30,000 trucking companies in the United States. More than 10 million drivers have commercial licenses nationwide, about a quarter of whom hold permits to haul hazardous materials, like gasoline and other dangerous chemicals or agents.

More than 800,000 shipments of hazardous materials are made daily, roughly 80 percent by fuel trucks, the Transportation Department said.

"No scenarios, no theory is too far fetched - we must reexamine all standards and safeguards to protect passengers and ensure the safe transport of goods and materials," Sen. John Breaux, a Louisiana Democrat, said.

The Senate panel pressed Transportation Department officials on why long-standing congressional safety and security recommendations have not been implemented.

One lawmaker suggested Congress should consider stripping the agency of its powers to regulate trucking if it did not take swift action to tighten regulations on licensing and oversight.

"The federal agency overseeing trucks has dragged its feet for years on installing the kinds of safety nets needed to help shore up our system," said Joan Claybrook, a former chief highway safety regulator and current president of consumer group Public Citizen.

Late in the day, Transportation Secretary Norman Mineta proposed to Congress that his agency be given greater oversight of hazardous materials shipment.

MORE TRAINING

Mineta wants to strengthen agency authority to inspect certain packages, streamline federal regulations on hazardous materials, and expand training for those involved in hazardous materials transportation.

One senior official with the Federal Motor Carrier Safety Administration, which regulates trucking, said after the hearing that federal inspectors are visiting "high risk, high volume" carriers, rental companies, hazardous materials distributors, and state and local governments to press heightened security measures.

"We want to make sure that drivers are properly credentialed and documented," the official, who did not testify, said.

The industry has initiated new background checks and has designated specific drivers for certain loads and routes.

Some companies have reevaluated their overall security procedures for pick-up and delivery, and have changed other aspects of their operations.

Truckers are being told not to stop and help motorists unless they are faced with a clear emergency.

They also have been advised, whenever possible, to avoid highly populated areas when hauling hazardous materials and make sure that type of cargo remains sealed at each stop.