Electronic motorway tolling is five or six years from becoming reality, it emerged this week.
Systems developed by two groups, down from seven which expressed interest, are midway through trials at the Transport Research Laboratory in Berkshire.
No-one involved in the trials would this week express an opinion about a likely start date for the next phase, a live trial at junction six of the M3.
The two consortiums, led by GEC-Marconi and Bosch, use 5.8GHz microwave links to communicate with transponders in vehicles on the motorway and deduct toll charges automatically.
Because there are likely to be different rates of toll for different vehicle types, a workable system must be able to recognise them and correlate this with the transponder information.
It must also be able to detect vehicles attempting to escape tolls. All the systems should achieve near 100% accuracy.
Trials of the Bosch system are complete and GEC Marconi’s system began tests, expected to last 10-16 weeks, on Tuesday.
A report will be produced by midsummer. Depending on the outcome, a ministerial decision will be made on whether to go on to the next phase, the M3 trial.
Sources close to the tests said that following this a larger scale motorway trial would be needed before a procurement decision could go ahead.
The whole process would take at least five or six years it is said.
GEC Marconi’s head of engineering for telematics and advanced systems, Tim Wander, said that the technology for communication between a fixed transponder and a moving vehicle was proven.
Classification technology has yet to be successfully demonstrated. But the firm was confident that its system could detect vehicle length and width to an accuracy of 10cm.
It could be configured to discriminate between as many as 10 different classes of vehicle, though four levels – motor cycle, plus light, medium or heavy vehicles – would probably be sufficient.