Which of the following best describes the applicability of the subchapter regarding CNG systems?

The correct choice emphasizes that the subchapter specifically pertains to CNG fuel supply systems designed for vehicular internal combustion engines. This focus is crucial because the regulations and guidelines established in this subchapter are tailored to ensure safety, performance, and compliance within the context of CNG usage in vehicles.

Understanding the distinction is important for compliance and operational safety since CNG systems for vehicles have different requirements compared to stationary installations or other fuel systems. These specifications ensure that the systems effectively handle the distinct challenges posed by the use of CNG in transportation, such as pressure requirements, fueling processes, and emissions.

By restricting the applicability to vehicular internal combustion engines, the regulations can be more precisely developed to address the specific needs and safety concerns associated with this mode of fuel use.