BILLINGS, Mont. — The federal government predicts that trains hauling crude oil or ethanol will derail an average of 10 times a year over the next two decades, causing more than $4 billion in damage and possibly killing hundreds of people if an accident happens in a densely populated part of the United States.
The projection comes from a previously unreported analysis by the Department of Transportation that reviewed the risks of moving vast quantities of both types of fuel across the nation and through major cities.
The study completed last July took on new relevance last week after a train loaded with crude derailed in West Virginia, sparked a fire, and forced hundreds to evacuate.
A full-scale federal investigation of the West Virginia derailment has begun as work continues to remove the overturned tank cars from the site. A fire sparked by the Feb. 16 derailment in Mount Carbon prevented investigators from gaining full access to the crash scene until this weekend. Foul winter weather also has hampered the investigation.
Monday’s accident was the latest in a spate of fiery derailments, and senior federal officials said it drives home the need for stronger tank cars, more effective braking systems, and other safety improvements.
‘‘This underscores why we need to move as quickly as possible getting these regulations in place,’’ said Tim Butters, acting administrator for the Transportation Department’s Pipeline and Hazardous Materials Safety Administration.
The volume of flammable liquids transported by rail has risen dramatically over the last decade, driven mostly by the oil shale boom in North Dakota and Montana. This year, rails are expected to move nearly 900,000 car loads of oil and ethanol in tankers. Each can hold 30,000 gallons of fuel.
Based on past accident trends, anticipated shipping volumes, and known ethanol and crude rail routes, the analysis predicted about 15 derailments in 2015, declining to about five a year by 2034.
The 207 total derailments over the two-decade period would cause $4.5 billion in damage, according to the analysis., which predicts 10 ‘‘higher consequence events’’ causing more extensive damage and potential fatalities. If just one of those more severe accidents occurred in a high-population area, it could kill more than 200 people and cause roughly $6 billion in damage.