Carmakers are also working on electric car models, which will be whirring onto our streets in the coming months. John Reedreports
In fits - and after some false starts - electric cars will begin appearing in growing numbers of world cities over the coming year, along with more of the recharging infrastructure needed to make them viable.
While General Motors and Toyota, the industry's two largest producers, hasten to develop viable plug-in hybrid petrol-electric cars, Daimler plans to roll out an all-electric version of its Smart Fortwo minicar in the UK capital on a trial basis next month.
But electric cars - a holy grail for clean-energy advocates - have not yet been commercially developed on a large scale, because of constraints relating to their batteries and publicly available recharging infrastructure. Earlier electric-car prototypes tested by Ford, GM and other makers foundered for various reasons.
Now pressure from public opinion and green-minded legislators, in places such as London and California, plus the success of conventional hybrid cars, such as the Toyota Prius, are pushing carmakers to intensify their plug-in electric-car efforts.
While Smart's tiny pilot cars will be powered by conventional nickel metal hydrite batteries, it and other carmakers are pushing manufacturers to develop the lithium ion batteries needed to extend driving range.
Concerns remain over the batteries' cost, size, and safety, because of their tendency to overheat.
Carmakers are also grappling with business models that will allow drivers to recharge their vehicles, and pay for the power, while in transit.
Bob Lutz, GM's vice-chairman for product development, said last week that the carmaker planned to prove the feasibility of its Chevy Volt plug-in hybrid electric concept car by next spring.
Toyota this month began testing its plug-in hybrids in Japan, California and France.
In September, the Japanese carmaker and French utility EDF announced a partnership to develop public recharging infrastructure on roads and in car parks. EDF and Toyota also said they had developed an "innovative charging and invoicing system" in the carmaker's test vehicles.
Yet because of challenges relating to batteries, Toyota says it will not produce plug-in hybrid cars "for several years".
In the US, former SAP executive Shai Agassi recently raised $200 million for Project Better Place.
The company plans to develop a network of car-recharging points and exchange stations that would allow motorists to swap their cars' batteries for recharged ones. To make its proposed "smart grid" for electric cars viable, the companies plan to focus on cities and small or "island" nations.
Renault said this week that it was discussing electric-car projects with partners including Mr Agassi.
Carlos Ghosn, Renault and Nissan's chief executive, said last month that the carmakers hoped to begin selling electric vehicles by 2012.