Stephen Russell, chief executive of the Celadon Group, an Indianapolis trucking company, says he understands why federal regulators want to take special precautions in a post-9/11 world by making new rules that check whether truck drivers are a threat to homeland security.

"We are well aware that certain explosives could be used to take down a building," he told a recent House Homeland Security subcommittee oversight hearing, speaking for the American Trucking Associations. But he noted that explosives on the government's hazardous materials list might also include large shipments of air-bag components or emergency flares, which pose no significant security risk.

Likewise, Russell added, products such as soft-drink syrup, batteries, matches and paint, which also are on the hazardous list, "do not represent any more threat to our homeland than carrying a truckload of bread."

The rule in question was issued in May 2003 by the Transportation Security Administration after the 2001 Patriot Act directed states not to issue operating licenses to truckers unless it is clear the driver does not pose a security risk.

Trucks haul about 8,000 shipments of hazardous materials daily, which is about 15 percent of truck tonnage annually. Potentially, the rule affects 2.7 million drivers, according to the TSA.

The rule requires a "security threat assessment," including fingerprinting and an intelligence and immigration check, for drivers hauling any of 3,000 commodities that the Department of Transportation lists as hazardous material when they reach certain quantities. Haulers of these materials in the past had to have a special "hazmat endorsement" in addition to a commercial drivers' license, but the qualification involved a written test and was directed toward safety issues -- such as what to do in case of a spill and the alerting of emergency personnel.

Drivers can be disqualified for a broad range of problems and offenses. Since Jan. 31, the TSA has disqualified 700 of 136,000 applicants.

As Russell put it, the crux of the problem for truckers is the security rule's adoption of this safety-oriented hazardous materials list, which has been in existence for decades and is updated regularly. It includes nine classes of substances including explosives, flammable solids, liquids and gases, and toxic, radioactive, corrosive and infectious materials.

The trucking industry would like to narrow the list to items that it considers a terrorism threat, while letting others such as paint, matches and nail polish be treated differently. The net effect would be the creation of a two-tier list, which would mean fewer drivers would face the strictest controls.

The industry complains the background-check system set up by the TSA is duplicative for drivers who already have security clearances. And a trip to a fingerprinting station might mean a detour of hundreds of miles to a state or federally run center.

"I only half-jokingly say that I have been through so many background checks, I might as well publish my fingerprints," said Michael Laizure, an owner-operator who has transported hazardous materials for more than a decade and has security clearances with the departments of Energy and Defense. He has been fingerprinted six times by the government, he said.

The Teamsters union also has complaints: the costs to drivers (the fees range from $94 to $133, depending on the state), the broadness of the "disqualifying offenses" that could cause drivers to lose their licenses, and concerns that foreign drivers might not have to comply with the rule.

Amy Von Walter, spokeswoman for the TSA, said the industry is pushing for changes on how background checks are handled and which items on the list trigger a threat check. "We are working with them on that," she said. The agency is also examining how to reduce duplication of background investigations by various agencies.

Truckers such as Laizure and security analysts realize that no amount of list-checking will stop a terrorist who wants to hijack a truck or run it into a building. The solution? More secure places to park and letting drivers defend themselves on the road -- an issue he says no federal agency has addressed.

"Ironically, I have clearances to carry just about anything . . . . but I cannot carry a weapon in the cab of my truck," he said.

The subcommittee chairman, Rep. Daniel E. Lungren (R-Calif.), said in an interview that he wanted to review the effectiveness of the regulations for those running a truck and "wanted to hear, straight up, proposals to improve the program by targeting resources at high risk."

He questioned officials from the TSA and the DOT's Pipeline and Hazardous Materials Safety Administration, which have been gradually implementing the rule for the past two years.

Stephen J. McHale, former TSA deputy administrator who is now in private legal practice, said the rule does fit the risk involved, even if it's a bit overbroad.

"One of the early decisions was not to create a separate system and try to work with the DOT classification," said McHale, who worked on the rule. He said a separate list of items that pose security risks -- which many truckers favor -- would be too confusing and unwieldy for the industry and the government to administer.

Prasad Sharma, assistant general counsel for the trucking association, said the industry will push for the necessary legislative or regulatory change to narrow the list to only security-sensitive hazardous materials.