Bi-fuel CNG vehicle means a vehicle equipped with two independent fuel systems, one of which is designed to supply CNG and the second to supply a fuel other than CNG.
CNG fuel container means a container designed to store CNG as motor fuel onboard a motor vehicle.
CNG fuel system means all components used to store or supply CNG to a vehicle's engine.
Dedicated CNG vehicle means a vehicle equipped with one fuel system and designed to operate on CNG.
Dual-fuel CNG vehicle means a vehicle which is fueled by two fuels simultaneously, one of which is CNG and the second is a fuel other than CNG.
High pressure portion of a fuel system means all the components from and including each CNG fuel container up to, but not including, the first pressure regulator.
Service pressure means the internal pressure of a CNG fuel container when filled to design capacity with CNG at 20 °Celsius (68 °Fahrenheit).
49 C.F.R. §571.303