A vehicle gaseous fuel supply system includes a high pressure filter, a primary pressure-reducing valve, a solenoid cut-off valve, safety means, and a secondary pressure-reducing valve. The present method is characterized in that a pair of first sidewall spacers is firstly formed on opposite sides of a gate electrode over a semiconductor substrate, and then a pair of second sidewall spacers is formed, each of which formed on one side of each first sidewall spacer. The drive assembly includes a frequency variable generator with an input shaft driven by the engine and the electric motor electrically communicates with the generator to receive output power from the generator.