The recent buzz over hybrids and electric cars has overshadowed the massive investments global auto giants are making in fuel-cell vehicles — another near-reality dream car that some believe promises an ultimate zero-emissions society.

Japan plans to stay on the cutting edge of the accelerated race for green technology — including fuel cells — that has kept its automakers competitive even as rival gas-guzzling carmakers crumbled under the weight of the global recession.

But despite a lead in technology, some carmakers, especially from abroad, say costly and back-breaking legal barriers are making Japanese roads uninviting for testing their latest pollution-free cars.

General Motors Co. of the United States and Mercedes-Benz, an arm of Germany’s Daimler AG, have long been engaged in talks with Japanese authorities to bring in their latest fuel-cell vehicles with 700-bar high-pressure hydrogen storage tanks for a test run on public roads.

“Japan is waving a flag for eco-cars but why don’t they let these cars in,” said George Hansen, director in charge of fuel-cell commercialization at General Motors Asia Pacific (Japan) Ltd.

Fuel-cell vehicles, which are powered by electricity generated by a reaction between oxygen and hydrogen, have long been researched as an alternative to petroleum-powered cars since they only emit water vapor, have ample driving range and can be quickly refueled.

With global auto giants pushing to mass-produce the electric vehicles with fuel cells from 2015, Japan is also scrambling to lay the groundwork that will help to allay concerns on safety, production costs and lack of infrastructure like hydrogen fueling stations.

But while the country already has regulations on a 350-bar hydrogen tank system, the government is still in the process of setting up a legal framework for a 700-bar system, which promises a longer cruising distance.

As a result, automakers say they currently need to collect and submit massive volumes of data for a series of safety tests to obtain certification, a straining and foggy process that could cost over ¥100 million in total.

In GM’s case, the automaker needs to provide convincing data to verify the safety of a tank material that is not common in Japan — the key cause for stalled talks for certification.

“There is nowhere else in the world that requires this amount of money for a test vehicle,” said Masanobu Wada, managing director of the Japan Automobile Importers Association.

Combined with huge resources already spent in developing the fuel-cell vehicle, there is also no guarantee that the extra costs for data collection will bear fruit.

At home, Toyota Motor Corp. is among the few domestic automakers given approval for driving its FCHV-adv fuel-cell vehicle with a 700-bar system on public roads.

Both Toyota and Honda Motor Co., whose FCX Clarity with a lower pressure 350-bar system is available for lease in Japan, refused to provide any details on the certification process.

But several officials familiar with the negotiations said Toyota likely also waded through the same hurdles to obtain approval for its FCHV since both Japanese and foreign automakers are obliged to meet the taxing requirements for a test run on public roads.

“There are no legal shortcuts,” an official at a Japanese carmaker said on condition of anonymity. “The government does not have any guideline to evaluate the new technology.”

GM brought one of its fuel-cell Chevrolet Equinox vehicles to Japan around two years ago for a test run, but it still remains stationed for display at a government exhibition park in Yokohama.

The U.S. automaker currently has over 100 of these cars on roads worldwide, including the United States, Europe and South Korea.

“To be honest, we can’t just let our vehicle — our valuable asset — sit tight since it will decay if we don’t move it,” Hansen said.

But GM is no stranger in the process. It made similar investments when it was granted approval for its liquid hydrogen fuel-cell vehicle, the HydroGen3, in 2003.

And this time the situation is vastly different. The company, which made a rare speedy exit from bankruptcy proceedings in July, is eager to put on a greener face and keep its foothold in an environmentally conscious market.

“We’re not giving up,” Hansen said. “GM believes it’s important to have our cars driven in Japan.”

Japan, for its part, has been trying to relax some of its regulations while launching various demonstrations and projects to ensure safety. It is also one of the key players in efforts led by the United Nations to compile global standards for fuel-cell and other auto-related technologies.

“We are aiming for international harmonization so Japan does not isolate itself with unique regulations,” said Yasushi Takahashi, chief officer at the government-affiliated New Energy and Industrial Technology Development Organization.

“But these promotional activities (on fuel-cell vehicles) will come to an immediate halt if an accident occurs, so we need to be cautious in that sense,” he added.

Takafumi Imada, subsection chief in charge of hydrogen and fuel-cell promotion at the Ministry of Economy, Trade and Industry, also said each automaker for its part needs to specify concrete numerical targets that demonstrate the company’s long-term position on fuel-cell vehicles.

“We feel that they should clarify the role of their (fuel-cell) business and their firm commitment and resolve,” Imada said. “Only then can we begin talk on division between the public and private sectors on what each of us needs to do.”

But whether foreign automakers are willing to wait for those legal barriers to come down is another matter, especially at a time when many are turning their attention away from a shrinking Japanese market to vibrant auto demand in neighboring China.

“If Japan wants to lead in environmental technology, it needs to think more about what that really means,” GM’s Hansen said.

“Instead of simply making good technology and exporting it,” Hansen said Japan should exercise “soft leadership in translating various ideas (on paper) into action.”