Toyota Motor said on Wednesday that it had developed a plug-in hybrid vehicle (HV) and become the first manufacturer to have such a vehicle certified for use on public roads in Japan.

The vehicle certified by the ministry of land, infrastructure and transport uses - like earlier Toyota-developed hybrids - both a petrol-powered internal combustion engine and an electric motor.

But increased battery capacity gives it a longer electric motor-only cruising range and a battery charging device allows users to recharge the batteries using household electricity.

These features enable the vehicle to run more often in petrol-free, electric-only mode, such as on short trips in city driving.

The resulting fuel efficiency improvements mean lower CO2 emissions and less fossil fuel consumption and therefore reduced pollution. Charging the battery with less expensive night-time electricity lowers total running costs.

"Although challenges still exist in the development of pure electric vehicles, such as a limited cruising range and issues related to cost, TMC still views plug-in hybrid vehicles as a promising technology for allowing electricity to serve as a viable power source for automobiles and is committed to their continued development as a key environmental technology," the automaker said in a statement.

TMC plans to conduct public road tests in Japan with eight of the plug-in HVs to verify electric motor-only cruising ranges and optimal battery capacity. It also plans to provide the government with data for formulating testing methods for emissions and fuel efficiency and to consider TMC's measures for promoting plug-in hybrids and the use of electricity. There are also plans to conduct public road tests of the plug-in HV in the United States and Europe.

Toyota enjoys global leadership in the development of petrol-electric hybrids and has licensed its technology to rival automakers such as Ford and Nissan.

PSA has demonstrated prototype diesel-electric hybrids but still faces cost-reduction challenges to bring them to market at an acceptable price. In real-world driving here in Europe, some diesel-only-powered models are as fuel-efficient as Toyota's Prius hybrid.

Toyota officials told just-auto at a technical seminar in Germany last June that they were working on hybrids powered by both fossil and renewable fuels including diesel and corn- and wood-based ethanol, as well as plug-in technology.