Raley's, a large retail grocery company based in Northern California, began operating heavy-duty trucks powered by liquefied natural gas (LNG) in 1997, in cooperation with the Sacramento Metropolitan Air Quality Management District (SMAQMD). The US Department of Energy (DOE) Office of Heavy Vehicle Technologies (OHVT) sponsored a research project to collect and analyze data on the performance and operation costs of eight of Raley's LNG trucks in the field. Their performance was compared with that of three diesel trucks operating in comparable commercial service. The objective of the DOE research project, which was managed by the National Renewable Energy Laboratory (NREL), was to provide transportation professionals with quantitative, unbiased information on the cost, maintenance, operational, and emissions characteristics of LNG as one alternative to conventional diesel fuel for heavy-duty trucking applications.