Liquefied Petroleum Gas (LPG) vehicles perform almost as well as petrol cost less to run than both and are up to 10-times better for the environment than diesel. Alternative fuels rarely come so viable, as one million Italians will testify.

And it's good, too, providing a genuinely viable alternative to petrol and diesel. Today's motorists expect certain performance levels, and LPG engines perform surprisingly well. Independent tests may suggest a slight deterioration in real world performance against petrol equivalents when running on LPG (despite what some manufacturers may say), but the differences would be unnoticeable to most motorists. An LPG-powered Vauxhall Vectra SRi V6 this year won a challenge race at Silverstone against 15 similar but petrol-powered Vectras, the first time an LPG-fuelled car has won a race in the UK. The Nissan Primera Dualfuel 2.0 claims no reduction in maximum power, torque or top speed when running on LPG.

Being significantly cheaper to run, presumably we should all be flocking to buy LPG vehicles. There is an obstacle, though, in that converting an existing car to run on LPG can be in expensive, while new LPG-fuelled cars cost extra than petrol or diesel equivalents.