"As of December 2009, the U.S. had a fleet of 114,270 compressed natural gas (CNG) vehicles, 147,030 vehicles running on liquefied petroleum gas (LPG), and 3,176 vehicles running on liquefied natural gas (LNG).[4]"
"As of 2009 Argentina had 1,807,186 NGV's with 1,851 refueling stations across the nation,[2] or 15% of all vehicles;[32] and Brazil had 1,632,101 vehicles and 1,704 refueling stations,[2] with a higher concentration in the cities of Rio de Janeiro and São Paulo.[9][32]"
http://en.wikipedia.org/wiki/Natural_gas_vehicle