With more than 30 million cars on the road in the UK, getting rid of all of them for the sake of the environment is going to be a hard job. Easier, perhaps, to look for a greener motor.

Jim Agnew investigates the best, and worst, in eco-friendly driving.

Before the ice caps started melting, choosing a car was an easier thing to do. If you wanted to carry a lot of people, you bought a people carrier, and if you wanted to go fast, you bought a sports car.

But now the sea levels are rising and the world is warming up, there is an extra thing to think about - the impact of your car on the environment.

The problem is, the ice caps have been thawing out for far longer than most car manufacturers would like to believe, so recent attempts at making one of the least green industries in the world eco-friendly could be seen as too little, too late.

The result of the clamour to go green is poorly thought-out self-righteous green initiatives and hybrids which drink a bit less petrol but use batteries that can't be disposed of or engines that have to be scrapped after just 100,000 miles.

In ten year's time, today's hybrid owners will have traded up for a newer model and no one will want a secondhand one. By future standards, the oh-so-trendy Prius will seem halfcocked.

The result will be scrapyards full of batteries, leaving the environment paying the price.

Some of the big manufacturers have cottoned on to this. VW has just brought out the new BlueMotion range of diesels of which the Polo version emits 5g per kilometre less of CO2 than the best hybrid on the market. BMW have developed a hydrogen car which is quicker off the mark than its petrol equivalent. Even Hummer have had a go.

But these planet-saving autos are not without their critics. One does wonder to what extent these companies, and the celebrities who endorse their cars, actually care about the environment and how much is just clever marketing. But despite the pretty adverts and PR campaigns, there are those who are genuinely concerned - Gordon Murray, for example. The man who designed the famous McLaren F1, along with countless other racing cars, has repented his carbon-based sins and turned his hand to creating a genuine planet-saving city car, the T25, which dramatically reduces emissions over the entire lifecycle of the vehicle, including those emitted during manufacture.

He is not alone. The creator of the air car used to make Formula One Racers and the owner of the stunning Tesla (pictured above - electric, sexy and 0-60 in under four seconds) used to have a company that sent satellites into orbit.

As the saying goes, you have to know how to do something before you can work out how not to do it. So with those who know how to pollute the most working out how to pollute the least, we may actually be in quite safe hands.



The greenest drive of your life

  • G-Wiz
    This is Britain's most common, truly environmentally-friendly car. It is made of light materials to keep weight down and runs on electricity (remember to switch to green power before you plug in). As anyone who works in central London may have realised, there are a lot of these on the road - 900 to be precise, and that's just in the capital.

They have also been lowered in price to just under £6,000.

However, they do have their drawbacks - in a recent NCAP safety test they failed miserably, with the test car falling apart completely.

  • MDI Cat
    This little beauty is the world's first air-powered car. Developed by a French Formula One engineer, it runs on compressed air and is available in solely air-powered and hybrid models.

The version that runs on compressed air can do 68mph but has a range of only 125 miles.

The more practical hybrid uses petrol to fuel the on-board compressor and has a range of 2,800 miles. There is a rotary engine version of the motor being developed in Australia, which weighs only 60g and is currently being used in vast indoor grocery markets.

  • H2H Hummer
    Endorsed by California's Governator himself, the Hummer 2 Hydrogen (H2H) is America's attempt at going green. It has a six-litre hydrogen engine built in Germany.

Because converting a car to hydrogen decreases its power, Hummer fitted a supercharger to the engine in an attempt to boost it back up again, but it still only manages a relatively measly 180bhp. What's more, the hydro-tank lasts only 60 miles and, of course, you have to make the hydrogen first - very energy intensive. At least they tried, though.

  • Koenigsegg CCRX
    The petrol version of this Swedish supercar is one of the fastest money can buy, but the CCRX runs on the even more potent bio-diesel. So, unlike with hydrogen conversions, power is boosted to a staggering 1018bhp (the world's fastest production sports car, the Bugatti, racks up 1001bhp). As a result you can reach the national speed limit in 3.2 seconds and the acceleration won't cease until you reach 200mph. Great as long as you have the good kind of bio-diesel, not the choppingdown- rainforests-to-growfuel- crops kind.



Named and shamed: The worst polluters

  • Bugatti Veyron
    It may be the world's greatest automotive achievement but at its top speed of 253mph it guzzles fuel at a rate of a gallon every 1.9 miles.
  • Dodge viper SRT10
    With emissions of 488g/km of CO2 you will be struck off the green list within seconds - and you'll be stuck in the highest road tax bracket.
  • Bentley Arnarge RL
    Nearly half a kilo of CO2 is pumped out every mile from this £190,000 luxury car.
  • Mercedes s63 AMG
    At 355g/km they are not the worst offenders but when you consider all they do is ferry the rich around Soho at 10mph you realise how ludicrous they are.
  • Anything made before 1980
    Old cars really are the worst. Before this time, no one even knew what an ozone layer was, let alone global warming.