Sat-navs set to nag about speed limit

Sat-navs that warn drivers not to speed -- or can even slow the car automatically -- could be as little as a year away.

Drivers in London would be first in line for the technology that pairs sat-nav GPS with a digital map of the capital and its speed limits to tell drivers how fast they should be driving.

Transport for London (TfL) has been building the map for a year and it could be ready for use within one year, if new mayor Boris Johnson backs the initiative.

TfL is preparing to trial a more advanced system that slows speeding vehicles by reducing the throttle. The Intelligent Speed Adaption (ISA) system will be tested on ten TfL cars and vans.

Tom-Tom sat-nav users would be the first able to use the speed-notification system, but TfL says it is in talks with other sat-nav providers about using the map.

It will be the most comprehensive digital map in Britain and when finished will cover all roads within the Greater London Authority area.

A spokesman for TfL said: "This is the biggest scheme of its type in the country, we are working on a comprehensive map of every single road in the capital."

He said that if the ISA system goes ahead and is trialled successfully it could be rolled out to other TfL vehicles.

Chris Line, TfL's road safety chief, recently told the transport select committee that such systems could reduce motoring deaths.

He said: "Casualties are very much linked to speed, both numbers and severity of casualties... and going back to technology there is a definite role there to be played by having vehicles which actually keep to the speed limit.

"Perhaps longer term we can use vehicle technology to actually manage the speed situation."