The Office of Defects Investigation (ODI) is only aware of the one subject fuel container rupture incident on the subject vehicles that first prompted this investigation. The subject CNG fuel system and fuel container design, material, manufacture, assembly and performance appear to be consistent with certain other manufacturers of CNG vehicles and related items of motor vehicle equipment, and in accordance with standards in effect at the time of manufacture. Since the subject incident, new and revised industry standards have advanced CNG fuel system and fuel container integrity and safety. In 2019, NHTSA noted an extremely low failure rate of CNG fuel containers, in a notice of proposed rulemaking (NPRM) to amend the visual inspection labeling requirement in FMVSS 304. NHTSA also entered a strategic partnership project (SPP) with the National Renewable Energy Laboratory (NREL) to assess fuel system and fuel container integrity requirements in an effort to update FMVSS Nos. 303 and 304. In NREL's report, they provided several considerations that reflect minimum safety standards, as well as industry best practices, to harmonize applicable light-, medium-, and heavy-duty natural gas and propane fuel vehicle codes and standards.Given these activities and the low rate of CNG fuel container ruptures in general, and the lack of other incidents among the subject vehicle population, indicating a lack of a safety defect trend, NHTSA is closing this investigation. The closing of this investigation does not constitute a finding by NHTSA that no safety-related defect exists. The agency reserves the right to take further action if warranted by the circumstances.Please see the Engineering Analysis closing report for more information.