It is no surprise that central London suffers the worst traffic congestion in the UK, says research by Transport for London. Typically vehicles spend half their time in queues. The morning rat race peak of 7am-10am has 50,000 vehicles per hour - the equivalent of 25 busy motorway lanes. With the population forecasters predicting an extra 750,000 people living in the city by 2015, the queues are going to get longer and the air more polluted. Is London mayor Ken Livingstone's proposal of a £5 congestion charge going to alleviate the problem?

Based loosely on schemes in other cities, including Singapore, Toronto and Trondheim, congestion charging would mean central London would be a timed-toll zone where drivers are charged between 7am and 7pm. The charge applies per vehicle, per day, allowing limitless journeys through the capital. Weekly, monthly and yearly passes will be made available via various outlets but no discounts will be offered as incentives. But alternative fuel vehicles will be exempt.

The proposed controlled congestion zone (CCZ) will span around eight square miles with some 180 entry and exit points. The perimeters will be roughly from Kings Cross in the north to Elephant and Castle in the south, Tower Bridge in the east to Edgware Road in the west. Failure to comply will result in an £80 penalty, reduced to £40 if paid within 14 days. The whole set-up is estimated to cost around £200m including £100m of complementary traffic management measures being spent across Greater London over the next three years.

Transport for London is optimistic and claim the scheme will cover its costs in the first year alone as it is expected to raise £200m each year. By law this revenue has to be re-invested in transport improvements in London for 10 years from the start of the scheme.

The plans for CCZ have been controversial, and there are many vocal objectors. The public consultation came to an end last month and Livingstone has officially until the end of the year to mull over the findings before reaching a verdict. The chair of the Greater London Authority's transport policy and spatial development committee, says: "Our job is to make sure that the issue is properly considered, rather than saddling London with an ill-thought out scheme. No single policy has more potential for disaster or more potential to benefit London." If it is accepted CCZ will be introduced in January 2003.

So what will it mean for office workers who commute to work in cars? More than a third of those in greater London use a car to reach their job, says the latest Reed travel to work survey. There is no doubt that against this background congestion charges will affect the decisions people make about travel. However, with such big numbers of people travelling each day, the picture is a complex one. "There will need to be a lot more detailed research to examine traffic flows and to model the effect of different types and levels of congestion charges before useful predictions about the likely effects can be made," says Katy Nicholson for Reed Executive.

Simple maths reveals that a full time worker using a car to get to work will have to spend an extra £25 a week, a total of £1,300 per year for the privilege. (Car owners who live within the CCZ are exempt but will be required to pay a one-off £10 registration fee.) Parking costs, will of course, be an additional burden. The time restraints of the scheme also pose certain problems. Imagine for a moment what the capital will be like at 6.55am, will motorists be bombing through breaking for the border? And what of the evenings? Will drivers sit waiting at their wheels looking at their watches to see when the final hour strikes so they can race through to catch a West End show or meet a friend for a meal?

Consider the inequalities of the charges. For those living within the confines of CCZ life will be made a whole lot easier. But what about those outside it? Might there be increased congestion in those areas? "We're not overly impressed with the scheme at this stage," says an Automobile Association spokesperson.

Paul Watters, AA's head of roads and transports, adds: "At the moment a rosy picture - fewer jams, easier journeys, great public transport - is being painted. But what is needed is real information and guarantees instead of the sketches we get at present, about how these proposals will affect people's everyday lives."

Questions need to be answered. And Watters has plenty. "How much more congestion will there be in inner London around the ring road? Can real reductions in jams be guaranteed in the centre? How much better will public transport be for drivers, and how can improvement be assured? How long will it take for people to register their trips in town? Is the system robust enough to ensure it's not just honest drivers who pay up? And what percentage of revenue will be lost through collecting charges?"

So unimpressed are the AA that they have recently written to congestion charging director David Turner to formally object to the scheme. Mayor Ken, it would seem, has much mulling to do over the winter months.