WASHINGTON: General Motors, the US auto giant, has announced plans to launch a Chevrolet Impala sedan next year that can operate on either petrol or compressed natural gas.

The bi-fuel sedan will be the only one on the US market and will be able to switch from natural gas to petrol, so extending its range capacity compared with vehicles that run on natural gas alone, Reuters reported.

GM chief executive Dan Akerson said the vehicle will have a powertrain that will make the switch from compressed natural gas to petrol seamless and give it a driving range of up to 500 miles.

Cars powered by compressed natural gas emit 20% less greenhouse gases than conventional ones, he said, adding that GM has increased investment in natural gas powertrains to "satisfy the green needs of both the environment and the stockholders".

Selling mostly to commercial and government fleets and achieving sales of 750 to 1,000 in the first year would be considered "a home run", he added.

According to industry group Natural Gas Vehicles for America, there up to 135k natural gas vehicles in the US, compared with more than 16m globally, and that most of them are buses and other commercial or fleet vehicles.

As there are 168k petrol stations in the US compared with 1,350 natural gas filling stations – and only half of those open to the public – the market remains small.Yet Ford has started to convert its trucks and vans for specialist commercial companies and Honda sells a Civic powered by compressed natural gas.

Data sourced from Reuters; additional content by Warc staff