Hydrogen fuel cells technology for cars is already available, so why are we not using these vehicles yet?

An obvious answer is that car companies are not making them, apart from rare exceptions like the Honda FCX Clarity launched in 2008. It seems like electric cars - the rival green technology - is the only alternative that has been taken seriously when it comes to lowering the carbon footprint.

Now the UK government has launched a programme to assess the viability of such technology before activating a plan to support the production of hydrogen cars.

"Hydrogen fuel cell electric vehicles are increasingly being recognised as one of the viable options as we move to a lower carbon motoring future," said Business Minister Mark Prisk.

The initiative UKH2Mobility is also supported by 13 carmakers - including Toyota, Hyundai, Vauxhall and Nissan - as well as gas and infrastructure companies.

They will share they expertise and knowledge on hydrogen fuel cells technology in order to establish the investment required to make the cars a commercial success. The ultimate goal  would be to make the UK the main producer of hydrogen technologies.

"UKH2Mobility will bring together industry expertise to establish the UK as a serious global player in the manufacture and use of hydrogen fuel cell electric vehicles and the supporting infrastructure," said Prisk.

The investigation team is expected to deliver conclusions by the end of 2012 - if they have good news, fuel cell vehicles could be around in two or three years' time.

Didier Leroy, Toyota Motor Europe's chief executive said: "We plan to commercialise fuel cell vehicles in 2015 and to achieve this goal a hydrogen charging infrastructure will be required."

The only remaining question would be, are hydrogen cars truly green? In theory, with these cars you are only taking oxygen from the air and mixing it with hydrogen to create electricity, so there are no toxic residues. However, the way you produce the hydrogen needed may be not green. It is the same for electric cars: the car itself doesn't emit harmful fumes, yet the energy sources used to produce the electricity they use might be.