Research Project

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Natural Gas Systems


To assess if any changes are needed to the Federal Motor Carrier Safety Regulations (FMCSRs), Federal Motor Vehicle Safety Standards (FMVSSs), North American Standard Inspection Procedures, and out-of-service (OOS) criteria to address the use of natural gas (compressed or liquefied) as an alternative to diesel fuel.


Many regions in the U.S. do not meet the National Ambient Air Quality Standards, and consequently air-quality management districts are compelling commercial fleet owner/operators to switch to clean-burning alternative fuels instead of diesel. The most commonly available alternative fuel for commercial vehicles is natural gas (either compressed or liquefied). Natural gas engines produce 20 percent less greenhouse gas emissions than diesel, while meeting the 2010 U.S. Environmental Protection Agency emissions standards. Moreover, the U.S. Department of Energy in 2009 is targeting urban commercial delivery and single-unit trucks, as well as more buses, to use natural gas as an alternative fuel.


Currently, there are about 4,600 heavy-duty trucks, 5,800 medium-duty trucks, and over 20,000 transit buses operating on natural gas. However, the FMCSRs regarding natural gas have not been updated. Examples of changes needed are labeling of vehicles, height clearance requirements, inspection requirements, training requirements for mechanics, leak detection requirements, and conformance of the FMCSRs to National Fire Protection Association (NFPA) 52 (e.g., removal of the ban on compressed natural gas tanks above the passenger compartment). A literature review of current consensus-based codes, standards, and best practices has been completed. A review of incidents involving natural gas commercial vehicles has also been completed based on data from the Master List of Natural Gas Vehicles Incidents maintained by the Department of Energy and from the National Fire Incident Reporting System. By May 2012, all site visits and consultations with stakeholders (truck original equipment manufacturers, designers/makers of natural gas fuel systems, fleet owners/operators, commercial vehicle enforcement, and inspection agencies) were completed.


A report that recommends specific changes to the FMCSRs, FMVSS 304, North American Standard Inspection Procedures, and OOS criteria.


This project is completed. Period of performance was 15 months.


FY 2011: $90,000 - FMCSA Research and Technology


The final report was published and can be accessed at The report's recommendations were briefed to the 21st Century Truck Partnership on June 19, 2013.


M.J. Bradley and Associates

Updated: Thursday, January 8, 2015
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