US News and World Report has an article on speculation about the conversion of the US rail system to use LNG - Natural Gas Rolls Into World of Freight Rail
Diesel locomotives may soon go the way of the steam engine.
Liquefied natural gas, or LNG, may soon replace diesel in most of the country’s freight locomotives, the U.S. Energy Information Administration said Monday. “It’s still relatively much cheaper than the diesel-gallon equivalent,” EIA economist Nicholas Chase says. In fact, if LNG prices remain as low as they are, some rail companies believe the conversion could happen as quickly as “the dieselization revolution of the 1940s and ‘50s,” when huge numbers of trains were converted from steam to diesel, Chase says.