The following symbols, acronyms, and abbreviations apply to this part: ABT Averaging, banking, and trading.AECD auxiliary emission control device.AES Automatic engine shutdown.CD drag coefficient.CDA drag area.CFD computational fluid dynamics.CFR Code of Federal Regulations.CH4 methane.CO carbon monoxide.CO2 carbon dioxide.CREE carbon-related exhaust emissions.DOT Department of Transportation.EPA Environmental Protection Agency.ETW equivalent test weight.FEL Family Emission Limit.g grams.GAWR gross axle weight rating.GCWR gross combination weight rating.GVWR gross vehicle weight rating.GWP global-warming potential.HC hydrocarbon.ISO International Organization for Standardization.kg kilograms.m meter.mm millimetermph miles per hour.N2O nitrous oxide.NARA National Archives and Records Administration.NHTSA National Highway Transportation Safety Administration.NOX oxides of nitrogen (NO and NO2).PM particulate matter.PTO power take-off.RESS rechargeable energy storage system.RPM revolutions per minute.SAE Society of Automotive Engineers.SKU Stock-keeping unit.TRRL Tire rolling resistance level.U.S.C. United States Code.VSL vehicle speed limiter.WF work factor. [76 FR 57398, Sept. 15, 2011, as amended at 78 FR 36394, June 17, 2013]