WASHINGTON — The head of a rail safety group Wednesday compared a widely used train tank car to the recalled Ford Pinto in urging U.S. regulators to require upgrades that would prevent accidents like a Quebec derailment that killed 47 people.

Karen Darch, co-chairman of a coalition of communities around Chicago formed in response to a merger of railroads, said regulators dragged their feet in mandating safety improvements to the car, known as the DOT-111, amid evidence showing the tankers are more prone to rupture in a derailment than other types.

“Unfortunately, your combined track record has been less than stellar when it comes to improving the crash-worthiness of the DOT-111 tank car — the primary car used in the transport of dangerous hazmat like crude and ethanol in this country and in Canada,” Darch, mayor of Barrington, Ill., told a panel of Federal Railroad Administration and Pipeline and Hazardous Materials Safety Administration officials.

Regulators had known since 1991 that the rail car has “a high propensity to rupture in derailment scenarios,” she said in comparing it to Ford’s Pinto, which in the 1970s was recalled amid questions that a flawed fuel tank would catch fire in a rear-end collision.

In response to safety concerns, U.S. rail companies since 2011 have added safety features to new DOT-111s to reduce the risks of a spill or catastrophic accident. Regulators are reviewing whether more steps are needed.

Cheryl Burke, a rail safety executive for Dow Chemical Co. in Midland, Mich., said retrofitting all DOT-111s in use was “impractical if not impossible.”

While she said Dow supports efforts to make rail transport safe, tank cars can’t be expected to be “completely impervious to the substantial forces that occur in significant rail accidents, particularly high-speed derailments.”

Regulators should do a risk analysis to determine whether particular rail fleets should be upgraded, Burke said.

Deborah Hersman, chairman of the National Transportation Safety Board, said in a 2012 letter to regulators that the DOT-111 had a “high incidence of tank failures during accidents.”

According to the NTSB, about 69 percent of the U.S. rail tank car fleet are DOT-111s. A Canadian Senate committee said in a report this month the government should consider accelerating the phaseout of tank cars.

U.S. regulators are reviewing safety rules for transporting hazardous materials in response to the July 6 train derailment and explosion in Lac-Megantic, Quebec. Some of the 72 cars, which were carrying crude from North Dakota’s Bakken formation to a New Brunswick refinery, were DOT-111s.

U.S. and Canadian regulators this month imposed emergency rules designed to prevent trains that are parked and unattended from rolling free. The Federal Railroad Administration now prohibits operators from leaving trains hauling hazardous materials without an operator, unless receiving prior authorization, and requires employees to report to dispatchers the number of hand brakes used.

Canadian investigators have said that not enough force was applied to the hand brakes to the train in Quebec to keep it from moving.

The U.S. Railroad Safety Advisory Committee, which develops new safety standards and includes officials from the government, industry and labor unions, is also studying whether further actions are required. It is meeting Thursday to discuss the issue.

The panel convened Wednesday took public testimony about what changes regulators should make.

James Stem, national legislative director for Sheet Metal, Air, Rail and Transportation union, said railroads should be required to have more than one worker on a train.

The train in Quebec, which was operated by Montreal, Maine & Atlantic Railway Ltd., had a crew of one and was parked overnight when it broke free and rolled into the town, where it derailed and exploded.

The number of crude shipments by rail has increased by 443 percent since 2005. North Dakota accounts for much of the increase. About 75 percent of its oil heads to refineries by rail, with pipelines covering the remainder.

Robert Fronczak, assistant vice president for environmental and hazmat safety and operations at the Association of American Railroads, encouraged regulators to ensure shippers accurately describe the types of tank cars being used along with the cargo being carried.

Some rail operators may be using cars certified for the least hazardous loads to carry fuel that warrants a more robust rail car, he said. The government should provide some assurance that “the commodities being transported are being transported correctly and being declared correctly,” Fronczak said.

With assistance from Andrew Mayeda in Ottawa.