The AAR said Thursday 13,888 carloads of petroleum and petroleum products, or about 9.7 million barrels of oil, were delivered on the U.S. rail system for the week ending Dec. 12.
Although deliveries for the week were up from last year, they represented a 6.3 percent decline from the week ending Dec. 7.
So far this year, 679,338 carloads, or about 475 million barrels of oil, were delivered by rail, a 31.6 percent increase from the same period last year, the trade group said.
The Energy Information Administration, the statistical arm of the U.S. Energy Department, said domestic oil production averaged 8 million barrels in November, the highest for any month since 1988.
An accelerating pace of oil production in the United States has placed a burden on pipeline capacity, industry officials say. U.S. oil production has increased, in part, because of gains from states including Texas and North Dakota.
The AAR said its total for U.S. operations excludes deliveries from Canadian National Railway Co. and Canadian Pacific Railway.
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