Kei-jidosha, or 'Kei cars' are one of our favorite "forbidden fruits" here at Green Car Reports.

Strict tax, insurance and parking regulations in Japan result in vehicles designed to set dimensions and engine sizes. So specific are they to Japanese roads and market conditions, they're rarely sold outside of Asia.

There's one notable exception, however: Mitsubishi's i, or "i-MiEV" electric car. And some anaylsts predict that several other electric Kei cars are set to join it over the next few years.

While North America's Mitsubishi i has been expanded to better suit market requirements, other markets get the original, kei-based version.

It's no more than 11.2 feet long, 4.9 feet wide or 6.6 feet tall--the maximum limit for Kei minicars and commercial vehicles.

Engines are restricted to 660cc and a maximum output of 63 horsepower, though electric motors are now becoming an option, particulary for vehicles which typically spend most of their time in congested cities.

Research analysts Frost & Sullivan suggest that the Kei car market is set for continued marginal growth over coming years. Over 50 percent of cars on Japanese roads currently conform to Kei-car regulations.

Of those numbers, say researchers, electric vehicles will play an increasing role.

Positive reception to the Mitsubishi i--including the part it played in ferrying relief and assisting infrastructure in devastated areas of Japan following 2011's Tsunami--has encouraged other Japanese carmakers, including Daihatsu and Suzuki, to develop their own electric Kei vehicles.

The Japanese government is offering financial incentives and tax exemptions to promote the use of electric vehicles, in common with many countries. Japan also wants 2 million regular charging stations and 5,000 rapid-charging stations along major routes by 2020.

The country still has several challenges to overcome when it comes to powering the next generation of electric cars--not least discontentment over nuclear energy after the Fukushima disaster--but the nation's roads and traffic conditions are more suited than most to electric power.

Would you want to see any more electric minicars? We're hoping for an electric version of the Honda N-One we recently drove in Japan...


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