 Natural gas vehicles (NGVs) are popular in regions or countries where natural gas is abundant.Widespread use began in the Po River Valley of Italy, and later became very popular in New Zealand by the eighties, though its use has declined., there were 17.8 million natural gas vehicles worldwide, led by Iran with 3.30 million, followed by Pakistan (2.79 million), Argentina (2.29 million), Brazil (1.75 million), China (1.58 million) and India (1.5 million).