WASHINGTON - U.S. and Canadian regulators have warned for years that the most widely used type of rail tanker is prone to rupturing during derailments.

Those warnings have taken on renewed importance after a runaway train that included the suspect rail cars and filled with crude oil crashed July 6 in a small Canadian town, setting off an explosion that killed at least 13 and destroyed 30 buildings in the city center.

The car, made by several manufacturers and known as DOT-111, ruptures more often in derailments than other models, investigators have said. The rail industry has opposed regulations proposed by agencies such as the U.S. National Transportation Safety Board that would require retrofitting to make leaks and fires less likely.

Smoke rises from railway cars that were carrying crude oil after derailing in downtown Lac Megantic, Quebec, Canada, Saturday, July 6, 2013.
Smoke rises from railway cars that were carrying crude oil after derailing in downtown Lac Megantic, Quebec, Canada, Saturday, July 6, 2013. (AP Photo/The Canadian Press, Paul Chiasson)

"During a number of accident investigations over a period of years, the NTSB has noted that DOT-111 tank cars have a high incidence of tank failures during accidents," NTSB Chairman Deborah Hersman said in a 2012 letter recommending tougher standards for the cars.

The train in the July 6 accident was hauling more than 70 carloads of crude oil from North Dakota to a refinery in New Brunswick. It crashed and burst into flames near the center of Lac-Megantic, in southeastern Quebec, forcing the evacuation of 2,000 people, police said.

At least 15 people were killed in the accident, with dozens missing. Canadian Prime Minister Stephen Harper said the scene resembled a "war zone" after touring the town, 155 miles east of Montreal, and 10 miles from the U.


S. border in Maine.

According to a NTSB report last year, about 69 percent of the U.S. rail car fleet is made up of DOT-111s. Those rail cars were part of the train in the derailment, Canadian Transportation Safety Board lead investigator Donald Ross told the Associated Press Monday.

Canadian Transport Minister Denis Lebel told reporters the cars involved in the accident make up 70 percent of the Canadian fleet. He said the train, operated by Montreal, Maine & Atlantic Railway Ltd., had been inspected the day before the accident and was found to be in good working order. Keith Stewart, climate and energy campaign coordinator for the environmental group Greenpeace Canada in Toronto, said the accident would probably show that government regulations haven't kept pace with expanding oil and gas development in North America.

"Up until now, the Canadian government has treated spills from pipelines and rails as a public-relations problem, and they need to start treating it as a safety problem," Stewart said in an interview.

An NTSB investigation into a June 2009 freight-train derailment in Cherry Valley, Ill., that killed one person concluded that flaws in the DOT-111 design probably worsened the spill. It noted that other models of tank cars designed to carry pressurized cargo have thicker shells and protected fittings and were less likely to leak in accidents.

"Of the 15 derailed DOT-111 tank cars that piled up in this accident, 13 cars lost product from head and shell breaches or through damaged valves and fittings, or a combination of the two," the NTSB wrote in its recommendations. "This represents an overall failure rate of 87 percent and illustrates the continued inability of DOT-111 tank cars to withstand the forces of accidents."

The agency recommended thicker shells and other modifications to strengthen the rail cars.

If retrofits couldn't be done, the NTSB suggested phasing out DOT-111 use for transporting hazardous materials. It has cited other accidents in which the performance of the tankers was called into question, including a 1992 derailment in Superior, Wis.; a 2003 one in Tamaroa, Ill.; and a 2006 incident in New Brighton, Pa.

The NTSB can only recommend changes to regulations to other agencies, such as the Pipeline and Hazardous Materials Safety Administration. The pipeline agency, part of the Department of Transportation, said it was still reviewing the NTSB recommendations on tank cars.

"We need to review these regulations and maybe increase them," Rep. Henry Waxman, D-Calif., said in an interview in Washington. "This ought to be a wake-up call."

In 1994, 23 freight cars on a Canadian National Railway Co. train derailed northwest of Sudbury, Ontario, and three DOT-111 tank cars spilled vinyl acetate, a liquid with a high fire hazard when exposed to heat or flame, according to the Transportation Safety Board of Canada.

"The susceptibility of 111A tank cars to release product at derailment and impact is well documented," the Canadian safety board said in a report on the Sudbury spill. "The transport of a variety of the most hazardous products in such cars continues."

In 2011, the Association of American Railroads told the U.S. Pipeline and Hazardous Materials Safety Administration that it supported updated rules for new tank cars, though it wanted existing ones exempt.

Patti Reilly, a spokeswoman for the association, said the group worked with tank car manufacturers on safety improvements to models built after October 2011 that will reduce the probability of a spill release during a derailment by 50 percent.

It could cost more than $1 billion to make some safety improvements to existing cars, according to the group.

By comparison, from 2004 through 2008, "derailments resulted in one fatality and 11 injuries, the release of approximately 925,000 gallons of these hazardous materials, and cleanup costs totaling approximately $63 million," the group said in a March 2011 filing with the pipeline safety agency.

Richard Streeter, an attorney representing the Village of Barrington, Ill., said the rail group is overestimating the cost of upgrades. Canadian National Railway runs through the heart of Barrington, which filed a separate petition with the U.S. Transportation Department last year asking that new and existing tank cars be built to higher standards.

"We took the position that the new rules should also require retrofitting," Streeter said in an interview. "Canadian National is building up the transportation of ethanol and crude oil, hauling it out of Canada. Guess where they're going through. It's kind of a scary proposition."

The debate comes as U.S. oil companies are relying more on rail lines to ship crude from places including North Dakota where pipeline construction hasn't kept pace with production. It wasn't until 2008 that producers in North Dakota began shipping crude via railroads. Now as much as 675,000 barrels of oil a day leaves the state by rail, according to Justin Kringstad, director of the North Dakota Pipeline Authority, which oversees pipeline development in the state.

Rail carries about 75 percent of the oil from North Dakota, now the second biggest producer in the U.S. behind Texas, with pipelines accounting for the rest. The Keystone XL pipeline proposed by TransCanada Corp. could carry as much as 100,000 barrels of oil a day from the state's Bakken formation.

Montreal, Maine & Atlantic said in a statement that the train, which was parked outside the town, was shut down by someone after the engineer left for the evening.

This "may have resulted in the release of air brakes on the locomotive that was holding the train in place," the company, a short-line carrier owned by closely held Rail World Inc. of Chicago, said.

"Until we know what happened it's hard to say with certainty that there is a regulatory lapse," Christine Tezak, managing director of ClearView Energy Partners LLC, said in an interview. "When you look at the phenomenal exponential growth of oil volumes moved by rail up until Saturday, the record was fantastic."