WASHINGTON — The explosion of a runaway oil train in Canada highlights the risks that come with transporting oil, no matter the method.Spills from rail cars occur more frequently than from pipelines but tend to be smaller. The Quebec disaster Saturday, which by late afternoon Monday was blamed for more than a dozen deaths, underscores a trend in which North America’s oil is increasingly transported by train. As production has grown from new shale fields and plans for new pipelines stall, existing lines struggle to keep up with demand. Since 2009, the number of train cars carrying crude oil hauled by major railroads has jumped nearly 20-fold, to an estimated 200,000 last year.For example, Fort Worth-based Burlington Northern Santa Fe said in a recent report that its petroleum-hauling business was up 69 percent in the year’s first six months, to nearly 250,000 carloads. That compared to its total carload increase of just 4 percent.U.S. railroads saw their petroleum shipments rise 27 percent in the same period, according to the Association of American Railroads, a trade group.Crude-by-rail activity is concentrated in North Dakota’s booming Bakken Shale, although Texas’ Permian Basin in West Texas and the Eagle Ford Shale in South Texas are seeing limited rail transport as production in those fields grows.Union Pacific, which operates a major rail yard in Fort Worth, said revenue from chemical shipments, which include petroleum but also other petrochemicals, were up 15 percent, “driven by growth in crude oil shipments from the Bakken, Permian and Eagle Ford shale formations primarily to the Gulf area.” It said that business rose three-fold from 2011.It’s not known how many rail cars carrying crude oil move through North Texas, but it’s likely limited, observers said, even allowing for the area’s standing as a major rail hub.“There’s not much crude by rail in Texas because there’s a lot of pipeline infrastructure in place,” said Bill Day, spokesman for San Antonio-based Valero Energy, a big refiner. But he agreed that “you’re going to see more and more overland shipments” as U.S. crude oil production outstrips pipeline capacity.The Canadian Railway Association estimates that as many as 140,000 carloads of crude oil will be shipped on Canada’s tracks this year — up from 500 carloads in 2009. The Quebec disaster, which involved Bakken crude on its way to a New Brunswick refinery, is the fourth freight train accident in Canada this year involving crude oil shipments.In a prepared statement, BNSF noted that “railroads remain the safest way to transport hazardous materials, reducing accidents by 91 percent since 1980 due to industry investment and operating practices, and BNSF is continuously assessing and improving its own operations to prevent incidents in the first place.”According to the Federal Railroad Administration, over the past 10 years, the number of rail cars containing hazardous material that were damaged or derailed declined by 38 percent.Kate Collarulli of the Sierra Club said pitting railroads against pipelines is a false choice. “To say we have to choose between rail and pipelines is cynical and defeatist,” she said, calling oil a “dangerous fuel” no matter how it is transported. Staff writer Jim Fuquay contributed to this report, which contains material from The Associated Press.