The Big Question: Can road pricing solve Britain's traffic congestion problem?

What is the London experience?

By far any away the biggest road toll scheme operates in London, so any debate about the introduction of a nationwide system will centre on the capital's congestion charge. Introduced on 17 February 2003, it was aimed at reducing traffic levels in the centre of the capital which had been reduced to walking pace for much of the day.

Transport for London estimates that congestion has been reduced by 30 per cent, and that emissions of nitrous oxides and particulates have been cut by 12 per cent. Carbon emissions have dropped by 20 per cent.

In considering a scheme to cover the whole of the country, its impact on traffic volume would clearly depend on the level of tolls. When the London charge was introduced, the price was set at £5. Last July, it rose to £8 and yesterday the Mayor of London, Ken Livingstone, indicated that it could increase to £10 in June 2008 if he wins a third term. Next February, the zone covered by the toll will double in size when it is extended westwards into Knightsbridge, Kensington and Chelsea.

How would it work outside London?

A report for the Government, Feasibility study of road pricing in the UK, estimated that a national scheme could cut congestion by half and save £12bn a year. The study suggested charges from 2.4p to £1.34 a mile, depending on when and where the motorist was driving. At 3am on a minor country road, motorists would pay the lowest tariff - possibly nothing at all. At 9 am on a Monday on the M25, drivers would pay the highest levy. The report insisted that only around 0.5 per cent of traffic would pay the highest charges.

Is the charge bad for business?

The London Chamber of Commerce believes opposition to the scheme has hardened. In a survey it conducted last year, the chamber found that 84 per cent of retailers reported their takings were down since the charge had been introduced and that 62 per cent of those said the toll was completely or mostly to blame. The pressure group London First says that if the Mayor of London were to drive through his plan to increase the congestion charge to £10, it would "decimate" retail businesses, especially in west London. But Transport for London argues that the impact on business has been broadly "neutral". It is also pointed out that a national toll would be unlikely to deter people from visiting one area because the whole country would be covered.

What is the scale of the problem nationally?

Traffic levels in Britain have risen 11.4 per cent since 1997, and last year topped 500 billion vehicle kilometres for the first time. The biggest increase has been on the motorways where traffic has risen by 19 per cent.

(In 2000, John Prescott, then the minister responsible for transport, famously remarked that the Government would have failed if it did not reduce road traffic.)

The costs involved in the different forms of transport have tended to encourage people to travel by car. The Liberal Democrats calculate that the real cost of motoring declined by 9 per cent between 1997 and 2005, while bus and coach fares rose by 15 per cent. Rail fares went up by an average of 5 per cent - making them among the most expensive in Europe.

What are the Government's plans?

Ministers believe it will be technically feasible to introduce a national system in around 10 to 15 years. The intention is that the charges would replace fuel duty, but the Treasury will be anxious that the plan will be revenue neutral - at the very least. Some motoring groups believe that it will be used as a wheeze to extract more money from the motorist.

On Wednesday the new Transport Secretary, Douglas Alexander, confirmed the Government's interest in a national system. He admitted there were "very big issues to be resolved", but set aside £10m for the private sector to work on the technology needed to bring in road pricing. Mr Alexander expects the initiative to lead to a pilot exercise in four or five years, although substantial strides in technology and a huge amount of political will are necessary before any scheme could be rolled out on anything like a nationwide level. It will be the biggest transport project ever attempted in Britain - and probably the world.

Some road-pricing enthusiasts are frustrated by the pace set by the Government. The Chartered Institute of Logistics and Transport is calling for a detailed timetable for its introduction. Without such a blueprint, Jim Coates, chairman of the institute's road capacity and charging forum, believes the Government's announcements could be seen as "empty rhetoric".

Are there any such schemes elsewhere in the world?

There is nothing on the scale of London's congestion charge. Singapore introduced a tolling system in a restricted zone in 1975 which was subsequently extended to the major expressways and to arterial roads.

In Melbourne, the 22km City Link Toll Road is an electronic toll road in the heart of Australia's second city. The authorities found that it had resulted in a reduction of 25,000 cars at peak times.

Norway's third-largest city Trondheim has introduced a toll for motorists entering the city between 6am and 6pm. Peak rush-hour traffic has dipped by more than 10 per cent.

In 1997, Toronto opened its 108km express toll route - the world's first all-electronic open access highway. The authorities say it has relieved congestion throughout the area's overloaded road system.

What technology could be used for a national scheme?

Automatic Number Plate Recognition uses high-definition cameras to record a vehicle's registration number, logged by date and time, which is then relayed to a central computer. This can be cross-checked against a database of registered users for charging purposes, or, in some cases, the vehicle's registered owner can be traced through DVLA data.

The "Tag and Beacon" system uses microwave radio beacons which interrogate tags or smartcards carried in vehicles. Passive tags merely provide basic information on the vehicle type or registered user.

The Global Positioning System is currently thought to be the ultimate technology, simply because it is usually highly accurate, and vehicle-specific details can easily be added to increasingly common SatNav devices.

Experts at the Chartered Institute of Logistics and Transport point out that the most essential feature is "inter-operability". In other words, the same technology should work wherever you are.

Is there an alternative?

It is a question of stick or carrot. The Government could increase car tax and fuel excise duty to reduce congestion, or they could make public transport cheaper and more reliable. After all, getting people out of their cars solves the congestion problem at a stroke. Ministers, however, seem to be intent on introducing the nationwide charge.