Autogas is shortly to commence a trial in London of a traditional black London taxi running on LPG.

The company, which has the largest network of automotive LPG refuelling pumps in the UK, hopes the cab will be approved by Transport for London for use later this year.

The vehicle, which has had its diesel engine replaced by a petrol engine converted to run on LPG, will be run by its drivers at Epsom Cars and Cabs 24 hours a day in order to speed up the process, which includes a 10,000 mile durability test.

Autogas believes the LPG re-powering solution will prove attractive to black cab owners who want to extend the working life of their vehicle in London rather than invest immediately in a brand-new one.

Paul Oxford, business development manager of Autogas, said: “Not everyone is going to rush out and buy a new vehicle straightaway. If someone is coming up to retirement, for example, why buy a new cab?

“By converting with an approved LPG system they can get another five years of service from the vehicle, as well as dramatically reducing air pollution and making substantial savings on fuel costs."

Currently London imposes an age limit of 15 years on black cabs with diesel engines. In contrast, approved LPG conversions can be exempted and allowed to run for another five years, up to 20 years old.

This provision is important in the run-up to 2018, when all new hackney carriages in London will have to be zero emission capable as part of the city’s drive to reduce air pollution. Taxis which are already licensed won’t be affected.

Birmingham City Council has already backed LPG as an alternative fuel which will help reduce air pollution in the city. Sixty-three of the city’s taxi fleet are being 'repowered' from diesel engines to petrol engines running on autogas LPG.

Initial emission testing at MIllbrook has shown the LPG technology produces 80% fewer NOx emissions compared with a normal diesel powered version, as well as a 99% reduction in sooty particulate matter.

At around 55p a litre, LPG is also cheaper than conventional fuels. Repowering of a taxi costs around £8,000 and takes around three days.