Furthermore, since the fuel has a very low density, piping the fuel across oceans or in cargo ships is impractical ensuring that gas demand is a very localized business. However, natural gas has seen some developments in this respect in the last few years thanks to the advent of Compressed Natural Gas or CNG. This fuel is generally considered ‘greener’ than gasoline and since it is very abundant in major gasoline consuming markets such as the U.S. some have called for increased reliance on the fuel for transportation.