By Tom Symonds
BBC transport correspondent
A BBC News trial of "pay as you drive" motoring suggests that some motorists with high mileage could face bills of more than £2,000 a year if the government presses ahead with its controversial road charging scheme.
This could result in drivers facing a potential charge for driving on any road.
Ministers say road charging could be a reality within 10 years
The news team has been monitoring the driving habits of four motorists from the West Midlands for a month to get an idea of the size of bills they could face.
We took a "white van man"; a "school run mum", a rural florist and a car commuter.
Our "white van man" Steve Coape-Arnold was shocked at his final bill of £194.31 - or the equivalent of £2,338 a year.
He said if road charging came in he would have no choice but to have to pass on the charges to his customers.
"We can't pick and chose the time we travel. We have to travel when the customer wants us to.
"It is basically just another charge. It's trying to price us off the roads."
On the other hand our car commuter Nick Waddington declared himself "pleasantly surprised" at his bill for £126.77 for a month - or £1,512 a year.
He makes a daily 32-mile journey into the Birmingham offices of Knight Frank where he is a chartered surveyor.
He says that if the roads became less congested as a result of road charging, he might be able to cut 20 minutes off his journey and spend more time either with his family or actually working.
Each of the vehicles in our trial had a satellite navigation system installed which transmitted data to Television Centre 24 hours a day, 7 days a week, giving a precise minute-by-minute location of which road the vehicle was on and either the speed it was travelling - or whether it was parked up with the ignition off.
The data was processed according to a road charging model drawn up by transport expert Professor Stephen Glaister of Imperial College, London.
The prices vary according to time of day and how congested the roads are.
They also take into account the impact on the environment and the number of road accidents - with a view to encouraging motorists to avoid congested roads at peak periods to keep their bills down.
Professor Glaister's prices range from 0p to 48p.
The BBC News scheme pre-empts road charging trials which the government intends to pilot within the next four to five years.
These moved a step closer this week when measures for enabling these trials to go ahead were announced in the Queens Speech.
The Transport Secretary welcomed the experiment
The Transport Secretary Douglas Alexander on Friday said road charging pilot schemes could be introduced within four or five years and road charging itself could become a reality within 10 years.
He welcomed the BBC News series as a valuable contribution to the debate.
He acknowledged: "I don't kid myself that there's widespread support at this stage.
"I think we need to tackle that. Firstly by having a national debate - and I welcome this week's series.
"At the same time I want to learn experience from local pilots which devise local solutions that tackle congestion effectively in local communities."
The news team chose the West Midlands for its experiment as it is one of the most congested areas outside London and is one of the areas bidding to undertake the governments pilots.