The Association of American Railroads (AAR) is calling on the U.S. Department of Transportation (DOT) to update regulations and require operators that use tank cars to transport flammable liquids — including crude oil and ethanol — to retrofit or phase-out older models and build new cars with more stringent standards.

Comments filed with DOT’s Pipeline and Hazardous Materials Safety Administration this month come after a string of high-profile accidents in which freight trains carrying crude oil have derailed (see Shale Daily, Aug. 22).

The AAR said that roughly 92,000 tank cars are currently moving flammable liquids, with approximately 78,000 of those requiring a retrofit or phase out based on its proposal.

Under the proposal, AAR is recommending improved design standards that call for new cars to include an outer steel jacket around the tank car and thermal protection, as well as full-height head shields and high-flow capacity pressure relief valves, among other suggestions.

AAR has said that the amount of oil hauled by rail in the U.S. rose more than 20-fold from 2009 to 2012, when 6.5 billion gallons were carried by train.

As exploration and production companies remain squeezed by limited takeaway capacity, as more pipelines slowly come online, that number is only likely to increase as they continue to turn to rail cars for more of their transportation needs.

“Freight railroads understand that the rail supply marketplace is seeing an increased demand for tank cars needed to move more flammable liquids, such as crude and ethanol,” said AAR President and CEO Edward R. Hamberger, in a statement. “We believe our suggested approach to improving tank car safety allows railroads to continue to serve their customers, while taking rail tank car safety to the next level.”