Japan's transport authorities have given Mazda permission to road test a hydrogen-fuelled, rotary-engine version of its RX-8 sports car.

This unique vehicle has a dual-fuel system that allows the driver to select hydrogen or petrol with the flick of a switch. In what could prove a historic event, this will be the world's first "street legal" dual-fuel hydrogen rotary.

The go-ahead from Japan's Ministry of Land Infrastructure and Transport (MLIT) comes 12 months after Mazda unveiled a hydrogen/rotary concept RX-8 at the 2003 Tokyo motor show. The car maker's near-term goal is to assess the practicality of this unique powertrain in everyday use. In the next-stage, expected within two years, test vehicles will be leased to governments and fleet users.

Known as H2RE, the test vehicle will deliver good performance with no loss of interior space for four people - the high-pressure hydrogen fuel tank is mounted in the vehicle's luggage compartment. The H2RE is powered by a modified rotary engine with electronically controlled hydrogen gas direct injection system on the rotor housing.

The engine has proved ideal for burning hydrogen as the intake area of a rotary stays relatively cool, reducing the tendency for engine backfire - a significant challenge in conventional engines. The hydrogen/rotary combination likewise offers superior environmental performance - zero emission of CO2 and near zero NOx emissions. And because existing parts and production facilities are used, the engine can be built reliably at a relatively low cost.

More importantly, the hydrogen/petrol dual fuel system will enable the H2RE to travel beyond the range of the few hydrogen filling stations now available. Mazda will continue to develop this technology for practical use.