With U.S. railways carrying more crude oil, Sen. John Hoeven, R-N.D., says more funding is needed for improved rail inspections.

"There is an increased need for improved rail inspections as one part of a comprehensive plan to improve rail safety for our communities," he said in a letter sent Thursday to members of the Transportation, Housing and Urban Development Subcommittee.

The National Transportation Safety Board said about 950 barrels of oil spilled when two trains operated by BNSF Railway collided and derailed near Casselton, N.D., in late December.

In January, the Pipeline and Hazardous Materials Safety Administration issued a safety alert saying the type of crude oil in the Bakken reserve area in North Dakota may be more flammable than other grades.

An increase in oil production in North Dakota has strained existing pipeline capacity, forcing energy companies to rely on rail as an alternate transit method.

The Association of American Railroads said Thursday about 1.1 million barrels of petroleum and petroleum products traveled by rail for the week ending March 29, an 8.6 percent increase from 2013.

For the year, 186,965 railcars, or around 13 million barrels, were delivered -- a 7.1 increase from last year.