By Ray Furlong BBC News, Berlin, Germany

Germany has a system similar to the one planned for the UK

But the system is now up and running, and relatively glitch-free despite warnings that it would lead to traffic chaos.

In Germany it applies only to lorries, not to cars. It also only applies to the autobahns, Germany's motorways.

This has caused some transport companies to send their heavy goods vehicles rumbling along smaller roads, upsetting the towns and villages along the way.

Trucks carry small black boxes in their cabins which communicate with infra-red sensors mounted on bridges that cross motorways Charge trials 'in five years'

The government is now thinking of expanding the scheme.

The system uses state-of-the art technology.

Trucks carry small black boxes in their cabins which communicate with infra-red sensors mounted on bridges that cross motorways.

Fines for dodgers

There are also cameras in place that can read number plates of vehicles that don't have the onboard units.

A central database is then able to track their progress across the country, charging an average of 12.5 euro cents (8p) per kilometre.

There are fines of up to 20,000 euros (�13,401) for fee dodgers.

The German government predicted the system would bring in 2.5bn euros (�1.68bn) in revenues each year but has not so far moved to reduce levies on fuel or other motorist-related taxes to compensate.