The use of liquefied natural gas (LNG) as a line-haul locomotive fuel is not a new idea, despite recent publicity, with previous work stretching back into the 1980s. Intense publicity has been given to recent announcements about developing dual-fuel locomotive engines which can burn natural gas as the primary fuel, using diesel fuel only as a pilot fuel for gas ignition. However, developing a locomotive engine capable of using gaseous fuel may prove to be only one of five major challenges to widespread adoption of LNG as a freight railroad fuel: 1. Dual-fuel line-haul locomotives with engines which can use natural gas fuel must be developed and made available for use. 2. Natural gas fuel must be made available to dual-fuel locomotives, either onboard the locomotive itself or by using LNG tenders coupled to the locomotives. 3. LNG must be stored and available for refueling dual-fuel locomotives or their tenders at logical locations along railroad corridors where such locomotives are to be used. 4. Natural gas (from gas fields or pipelines) must be available along with liquefaction plants to convert the gas into cryogenic LNG fuel. 5. The safe operation of trains and locomotives, and safe maintenance of rolling stock, is paramount and cannot be compromised (nor should the efficiency of the rail system) should dual-fuel locomotives and LNG tenders supplant or replace conventional diesel-fueled locomotives. For LNG to become an effective large-scale freight railroad fuel, all five factors must be managed jointly and treated as a 5-legged technology system. If any one of the five “technology legs” is weak or improperly developed, the entire LNG-based system may be unsuitable in the freight railroad environment.