A Toyota plug-in hybrid car design will begin testing on public roads in Japan, the company said Wednesday.

Toyota said its Plug-in HV, like previous Toyota hybrid cars, uses a gas-powered internal combustion engine and an electric motor. But it can operate longer in electric mode on short trips because of increased battery capacity, the company said, with a cruising range on the electric motor alone of about 13 kilometres, about four times as far as the Prius.

Toyota said it will conduct road tests on eight plug-in hybrids in Japan with plans for similar tests in the United States and Europe.

Other automakers, such as General Motors Corp. and Ford Motor Co. are developing similar plug-in hybrids. GM is working on the Chevrolet Volt plug-in hybrid, which it hopes will reach showrooms by 2010. Ford has been testing plug-in hybrids based on the Escape sport-utility vehicle, for one, but has not said when it plans to start mass producing them.

Plug-in hybrids, which also have an internal combustion engine, avoid the possibility with pure electric cars of losing the battery charge on the road, he said.

Mass production of plug-ins is so far being held back by costs and battery technology that limit the vehicles' range. Manufacturers are racing to bring the technology to market as consumers seek alternatives to traditional engines and high gasoline prices.

Although most automakers are working on hybrids, Toyota has the advantage of 10 years of experience in selling the technology, and in using feedback from drivers to make improvements, rather than relying on information from labs.

Toyota has placed a large emphasis on hybrid technology: it offers several other hybrid models, including the hybrid Camry and hybrid Lexus models. It has set a target of selling a million hybrids a year as soon as possible after 2010.

The more common hybrids, such as the Prius, switch between an electric motor and gas engine to deliver better mileage. They don't need to be plugged in to recharge because they recharge the motor as they run converting the energy from the wheels and braking.

In June, Toyota said its cumulative sales of hybrids passed one million vehicles, a landmark for the automaker that started selling the Prius a decade ago and now dominates the hybrid market.

With files from the Associated Press