Is satellite car-toll tech ready for prime time?

The Conservatives have raised concerns over the technology behind the government's plans to cut congestion by charging motorists for every mile they travel.

Under the proposals outlined by Transport Secretary Alistair Darling, drivers would be charged for every mile of their journey. The price would depend on the level of congestion and satellite tracking would be used to enforce the toll.

Prices would start at around 2p per mile on quiet roads outside of rush hours and go up to £1.34 per mile on busy motorways at peak times.

A pilot scheme could be set up within five years and the system could be rolled out within 10. There are currently around 30 million cars on the road in the UK.

But the Conservatives said there are still concerns around the technology behind the system.

Shadow Transport Secretary Alan Duncan said: "There are also key questions about the technology surrounding the scheme. We know that the government is struggling to develop a charging system for lorries. What is the status of this 'spy in the sky' technology?"

Duncan added: "How will the government deal with the civil liberties issue when Big Brother can trace your every move?"

Yet Robin Duke-Woolley, director of analyst house e-principles, said the technology is already being used successfully in Germany.

Since the start of the year, the satellite-based 'Toll Collect' system has been charging trucks using Germany's autobahns €0.12 per kilometer, with 400,000 vehicles now using the system.

"The principles of the technology are being proven on a fairly massive scale. I think this is more a question of the politics - that's why they are thinking 10 years away," he said.

"It has nothing to do with the technology not being here because it is. It is much more a political timescale than a technical one," he added.