MBSL65fan: not only in Europe. You can mount the LPG-system in all cars with fuel-engines.
So many of the big US-made SUV's and Pick-ups over here have LPG, too. In Germany the price of LPG is around half of the 95-octane fuel.
In the Netherlands LPG is very popular, you can get it at nearly every just middle-sized gas-station.