The amount of U.S. oil shipped by rail rose 9 percent during the first seven months of the year compared to 2013, reaching 16,000 carloads per week in July, according to the U.S. Energy Information Administration (EIA). U.S. crude oil production reached an estimated 8.5 million barrels per day in June for the first time in 18 years and is driving the increase in rail transport, the EIA said. Only 3 percent of petroleum shipped by rail in 2009 was crude oil; now crude accounts for more than half. Over the past three years, much of the oil has come from the Bakken Shale, primarily in North Dakota. Between 60 and 70 percent of the more than 1 million barrels per day of oil produced in North Dakota has been transported by rail so far in 2014, according to the North Dakota Pipeline Authority. The demand for rail cars has created a backlog that’s been particularly worrisome for farmers, who say their grain is rotting before shipping space is available to take it to market.