A U.S. safety official said Wednesday that the rail tank cars being used to ship crude oil from North Dakota's Bakken region are an "unacceptable public risk," and even cars voluntarily upgraded by the industry "may not be sufficient." National Transportation Safety Board (NTSB) member Robert Sumwalt told a House of Representatives subcommittee that the cars, known as DOT-111s, were involved in derailments of oil trains in Casselton, North Dakota, and Lac-Megantic, Quebec, just across the U.S. border.
