By Kev Kiernan
The most desirable green transport of the future may turn out to be powered by hydrogen and water vapour, rather than electricity.
Automotive firms Hyundai, Toyota and Honda are all in the final stages of developing hydrogen-powered vehicles for the general market.
Next spring will herald the first of the three; an SUV called Tucson by Hyundai which was displayed at Los Angeles Auto Show. The Tucson will initially only be available for public lease.
Honda announced similar plans at the same motor show, with its hydrogen vehicle expected in 2015.
Toyota recently appeared at Tokyo Motor Show with a promise to bring out a hydrogen-powered car in Japan by 2015.
Same range as petrol
Unlike electric vehicles, hydrogen vehicles can be refuelled quickly and have the same distance range of a typical petrol car.
It is also said that hydrogen technology has been improved significantly over the past few years to overcome safety and reliability problems.
The only problem currently is that very few hydrogen refuelling stations exist.
Another downside is the high costs car makers will be charging people to buy a hydrogen vehicle, pricing out the majority of motorists with outlays in line with those of today's luxury cars.
At Tokyo Motor Show, Toyota said it would be charging between £31,000 and £62,000, similar to its Lexus luxury sedan car.
Back in Los Angeles, Hyundai says it will lease its Tucson models for £312 a month over three years, with a £1,800 deposit required first.
It is, however, offering to pay the cost of the hydrogen fuel as well as of paying for any maintenance.
Hydrogen fuel stations
Hyundai says it will use Los Angeles because that is where most of California's nine hydrogen fuel stations are located.
The south-western US state says it has allocated £62.5 million to build 100 more refuelling points.
Honda refused to disclose the prices it plans to charge people, although it has been leasing fuel-cell cars since 2005.
It unveiled a prototype at Los Angeles Auto Show which has a range of 300 miles, to give people an idea of what it would look like.
Honda marketeer Stephen Ellis refused to say where the firm would sell its vehicles but implied that Los Angeles and states in the north-east of the US are favoured.
Advantages over battery cars
Paul Mutolo, from Cornell University Energy Materials Centre in New York state, said car companies have maintained their research into hydrogen power over the past decade.
That's even though battery-powered and hybrid-electric cars became more prevalent.
Hydrogen cars, Mr Mutolo said, have an advantage over battery-powered electric cars because drivers do not have to worry about running out of electricity and having to wait hours for recharging.
"It's very similar to the kind of behaviour that drivers have come to expect from their gasoline cars," he said.