"It's an accident waiting to happen. It's going to be a mess and we don't know where that mess is going to be," Schafer said.
For oil companies, the embrace of rail is a matter of expediency. Oil-loading rail terminals can be built in a matter of months, versus three to five years for pipelines to clear regulatory hurdles and be put into service, said Justin Kringstad of the North Dakota Pipeline Authority. Although more pipelines are in the works, he said moving oil by rail will continue.
The surge comes at the right time for railroads: Coal shipments — a mainstay of the rail industry — have suffered because of competition from cheap natural gas.
In the eastern U.S., CSX and Norfolk Southern railroads haven't seen as much growth because oil from the Marcellus Shale area of Pennsylvania, Ohio and New York is close enough to refineries that trucks haul the crude.
Yet BNSF is beginning to haul Bakken crude east to Chicago, where it hands off the tank cars to CSX or Norfolk Southern for delivery to Eastern refineries. It has also sent oil to the West Coast, a trend that could increase if Alaska crude production falters, as some industry observers are predicting.
The growth will require significant upgrades to already congested rail lines, industry analysts said.
Overall, crude oil shipments still represent less than 1 percent of all carloads. And there are far more dangerous materials aboard the nation's trains, including explosives, poisonous gases and other industrial chemicals.
But emergency officials are increasingly wary of major accidents involving oil trains, which carry far more cargo than some other hazardous-material trains.
While oil is not as volatile as some other products, a rupture of just one car can spill 20,000 to 30,000 gallons, said Sheldon Lustig, a rail expert who consults with local governments on accidents and hazardous materials.
Recognizing the risks, Houston-based Musket Corp., an operator of oil train terminals in North Dakota, Wyoming, Colorado, Utah and Oklahoma, has donated spill equipment and provided training to fire officials.
"You want to be a good steward in that community," said Musket managing director JP Fjeld-Hansen.
Federal Railroad Administration officials said they have coordinated hazardous-material training seminars and sought more law enforcement patrols for rail crossings to increase safety.
Federal law requires railroads to select hazardous-material routes after analyzing the potential for accidents in heavily populated areas and environmentally sensitive spots. Those analyses are confidential for security reasons.
Lustig said the railroads have considerable sway over the process.
"Under federal guidelines, the railroad makes the analysis, the railroad decides what they want to do, and the railroad does it," he said. "There is no public accountability."
Funk reported from Omaha, Neb. Associated Press writer James MacPherson in Bismarck, N.D., contributed to this report.