The American Petroleum Institute said proper classification of crude oil is essential when considering policies for safer rail transit.

In May, API said a study published by the North Dakota Petroleum Council eliminates some of the speculation surrounding Bakken crude. NDPC said Bakken crude oil "poses no greater risks than other flammable liquids" authorized for rail transport, though concerns have been raised by federal regulators

"Proper testing, classification and handling are important when shipping any material subject to PHMSA regulations, and crude oil is no exception," API President Jack Gerard said in a statement Thursday.

API published its own set of recommendations for testing and classification of crude oil for rail shipments, which includes a unique crude oil sampling and testing program.

U.S. regulators in January issued an advisory warning Bakken crude oil may be more prone to catch fire than other grades. For rail itself, the Department of Transportation in July called for the eventual elimination of older rail cars designated DOT 111 used to ship flammable liquids, "including most Bakken crude oil."

"This particular standard is one element of a much broader approach to safety improvement," Gerard said.