The UK took another step towards the introduction of automatic speed limiters, with a new trial starting within London that sees a bus, a taxi and cars all fitted with a device.

Earlier trials, back in 2008, suggested that lives could be saved by the Intelligent Speed Adaptation devices, which uses GPS to find out the local speed restrictions and limit the vehicle's engine.

Although the system can be overridden at the touch of a button, or switched off entirely in the current trial, there are inevitable fears that the system may be made mandatory in the future, and that limiting speed could prove dangerous.

Green light in London

However, Transport for London (TfL) is seeing for itself if the scheme works with some of its public transport vehicles.

Chris Lines, Head of TfL's road safety unit, told the BBC: "We know the technology works, and now we want to know how drivers in all types of vehicles respond to it.

"ISA is intended as a road safety device, but if Londoners embrace this technology we may well see additional benefits including reduced congestion as a result of collisions, and reduced vehicle emissions, as drivers adopt a smoother driving style."

The six-month trial will ascertain if the scheme can be rolled out further, with Southwark council already expressing an interest in fitting ISA to more than 300 of its vehicles.