LNG is typically used on medium and heavy duty vehicles and the tanks are most commonly found attached to the frame rails.However, in some instances they may be located behind the cab.LPG Tanks:In passenger vehicles, the tank is located in the trunk, or where the gas tank is usually found.In vans or pickup trucks they may be underneath or in the bed.In medium or heavy duty applications they can primarily be found along the inside or outside of the frame rail.