CONFUSED by the technical terms involved in alternative fuels? Here's a handy guide to finding your way around the subject:

Alternative fuel: A non-traditional fuel such as liquefied petroleum gas, natural gas or electricity.

Bi-fuel: A vehicle with tanks for two different fuels such as petrol and LPG.

CFV: Clean fuel vehicle. A vehicle that runs on an alternative fuel to petrol or diesel such as LPG, natural gas or electricity.

CNG: Compressed natural gas. This is the same as the gas that many people use for cooking, but stored in a compressed form.

CO2: Carbon dioxide. The greenhouse gas which is the main cause of global warming and climate change.

Converter: A company that can install extra equipment to a standard (such as petrol) vehicle to allow it to run on a clean fuel such as LPG.

Dual-fuel: Vauxhall's trademark name for its bi-fuel vehicles.

Fuel cell: A device that converts hydrogen into electricity, which can then be used to power a vehicle. Fuel cells produce very little or no pollution but are not yet commercially available - they're still the technology of the future.

Hybrid: A vehicle with an engine that can run on two fuels, such as petrol and electricity - like the Toyota Prius.

LNG: Liquefied natural gas. This is the same as the gas many people use for cooking, but stored in a liquefied form by reducing its temperature.

LPG: Liquefied petroleum gas; a mixture of propane and butane, currently the most widely used cleaner fuel in the UK.

NGV: Natural gas vehicle. A vehicle that runs on either LNG or CNG.

Nox: Oxides of nitrogen. A gas emitted by petrol and diesel vehicles which damages local air quality and leads to health problems.

PM: Particulate matter. Particles emitted by petrol and diesel vehicles which cause smog.

Particulate trap: A filter with a fine mesh fitted to a vehicle's exhaust system to capture particulates.