Liquefied natural gas (LNG) has been demonstrating its viability as a clean-burning alternative fuel for buses and medium- and heavy-duty trucks for the past 30 years. The first known LNG vehicle project began in San Diego in 1965, when San Diego Gas & Electric converted 22 utility trucks and three passenger vehicles to dedicated LNG.2 A surge in LNG vehicle project activity over the past five years has led to a fairly robust variety of vehicles testing the fuel, from Class 8 tractors, refuse haulers and transit buses to railroad locomotives and ferry boats.
Recent technology improvements in engine design, cryogenic tanks, fuel nozzles and other related equipment have made LNG more practical to use than in the 1960s. LNG delivers more than twice the driving range from the same-sized fuel tank as a vehicle powered by compressed natural gas (CNG). Although technical and economic hurdles must be overcome before this fuel can achieve widespread use, various ongoing demonstration projects are showing LNG's practicality, while serving the vital role of pinpointing those areas of performance that are the prime candidates for improvement.