U.S. regulators, acting after a oil train derailment last year ignited a fireball that killed 47 people in Canada, said they intend to require at least two crew members for crude shipments, a proposal opposed by the railroads.

The Federal Railroad Administration (FRA) also will establish minimum crew size standard for most freight trains and passenger rail lines, the agency said in a statement April 9.

“We are committed to taking the necessary steps to assure the safety of those who work for railroads and shippers, and the residents and communities along shipping routes,” Secretary of Transportation Anthony Foxx said in a statement.

The agency is acting after a train that was operated by one person was left unattended for the night in July and rolled into the center of Lac-Mégantic, Quebec, triggering a fatal explosion that destroyed half the town.

The Association of American Railroads, whose members include Berkshire Hathaway Inc.’s (NYSE: BRK-A) BNSF, said large railroads already run oil trains with at least two crew members.

Nevertheless, Edward Hamberger, the group’s CEO, said the FRA “has never shared an iota of data that shows or proves two-person crews are safer.”

“If a regulation is proposed, then the least that can be expected is that a federal agency should back it up with grounded data that justifies the recommend rule,” Hamberger said in a statement.

FRA administrator Joseph Szabo said in the agency’s statement that two-person crews would improve the safe transport of crude oil.

Crude-by-rail shipments have soared as oil drillers employ new technologies to crack open and free oil and gas from shale formations at a faster pace than pipelines can handle.

Canadian investigators found that the brakes on the Quebec train weren’t applied with enough force. Canadian regulators have since banned one-person train crews when hauling hazardous material.

“Whether a railroad is carrying crude oil through towns across America, or people taking a well-earned vacation or commuting to work, we need to make sure people are safe, whether on the train and near the tracks,” said Sen. Patty Murray (D-Wash.).

Murray is the chairman of the Senate Appropriations Subcommittee on Transportation, Housing, Urban Development and Related Agencies, which is holding a hearing on rail safety April 9.

Previously, the Department of Transportation ordered energy companies using rail to ship oil to test the chemical composition of all crude before loading it on tank cars. It is also studying whether rail cars carrying crude need to be made more robust to lower the risks that a derailment will cause an explosion.

Foxx told the subcommittee the oil industry has provided a minimal amount of data on the characteristics of oil from North Dakota’s Bakken Shale region, which is slowing down efforts to improve the safety of transporting the fuel. Bakken crude may be more volatile than other types of oil.