SEATTLE (AP) — Environmental groups asked the U.S. Department of Transportation to immediately ban shipments of volatile crude oil in older railroad tank cars, citing oil train wrecks and explosions and the agency’s own findings that accidents pose an imminent hazard.The petition filed Tuesday by the Sierra Club and ForestEthics seeks an emergency order within 30 days to prohibit crude oil from the Bakken region of the Northern Plains and elsewhere from being carried in the older tank cars, known as DOT-111s.Accident investigators have reported that the cars rupture or puncture during wrecks, even at slow speeds.Shippers in North America use about 66,000 of the so-called legacy tank cars to haul flammable liquids, including about 23,000 that carry crude, according to industry representatives.The Obama administration has said it will propose a new rule this month governing tank cars that could include retrofits of older cars and tougher standards for new ones.However, that “will take too long to address the imminent hazard posed by use of dangerous DOT-111 tank cars to ship crude oil,” according to the petition filed by the law firm Earthjustice on behalf of the two environmental groups.It could take a year before a rule is finalized. In the meantime, the shipments are putting small towns and major cities along the rail lines at risk, the petition said.Transportation Department spokesman Ryan Daniels said the agency cannot comment on whether an outright ban is under consideration, because a formal rule-making process for the older tank cars already is underway.Since 2008, derailments of oil trains in the U.S. and Canada have seen the 70,000-gallon tank cars break open and ignite on multiple occasions, resulting in huge fireballs. A train carrying North Dakota crude in DOT-111s crashed in a Quebec town last summer, killing 47 people.“We need to get them off the tracks as soon as possible.