Evaluation of Safety Standards for Fuel System and Fuel Container Integrity of Alternative Fuel Vehicles

The U.S. Department of Transportation (DOT) National Highway Traffic Safety Administration (NHTSA) is considering fuel system integrity requirements for medium- and heavy-duty natural gas and propane vehicles to update Federal Motor Vehicle Safety Standards (FMVSS) Nos. 301, 303, and 304. NHTSA is also considering updates to FMVSS No. 304 to address safety issues and to better reflect current best practices and existing standards for high pressure fuel tanks in motor vehicles. The National Renewable Energy Laboratory (NREL) conducted and attended subject matter expert panel meetings and other meeting types to develop recommendations for fuel system and fuel container integrity requirements for CNG and propane fuel vehicles. In addition, NREL completed a review of FMVSS Nos. 301, 303, and 304 against the latest editions of natural gas and propane international and industry codes and standards for the purposes of identifying commonalities and differing technical approaches as they pertain to natural gas and propane vehicle fuel system and fuel container integrity requirements. In this report, NREL offers recommendations to reflect current best practices and existing standards for light-, medium-, and heavy-duty CNG and propane vehicle fuel system container integrity, fuel container integrity, and fuel container fire tests. The recommendations for fuel system and fuel container integrity requirements are justified by literature review, relevant research, and technical forum feedback. In addition, this report provides relevant research, where available, and recommends test procedures to evaluate compliance with the performance requirements. The recommendations presented in this report for consideration are 1) update FMVSS to include fuel system integrity assessment of medium- and heavy-duty vehicles; 2) update FMVSS to include fuel system integrity requirements for propane vehicles and tanks; 3) add additional CNG fuel tank integrity tests; and 4) incorporate more repeatable fire test procedure for fuel tank integrity. Detailed recommendations are included in Section VII, and a summary of the line-by-line review of fuel system, fuel container integrity, and fuel container fire test requirements for natural gas and propane vehicles is provided in the appendices. This report also includes an overview of the regulatory landscape for natural gas and propane vehicles that was reviewed.