Two articles today ask the above question, with varying answers.
In the FT today Peter Hendy, Commissioner of Transport for London, admits that the Congestion Charge has not been an unfettered success:
Traffic snarl-ups in London have grown since the congestion charge was introduced almost five years ago, the man overseeing the scheme has acknowledged. But in an interview to mark the fifth anniversary of the tariff, Peter Hendy, commissioner of Transport for London (TfL), insisted that without it London would by now be in "serious trouble" as wider pavements, bus and cycle lanes, as well as protracted work to replace ageing water and gas mains, took their toll on the capital's car drivers.
Meanwhile, on the dawn of the £25 charge, the Independent evaluates the scheme:
About half the drivers who left their cars at home took public transport instead, with the rest getting a lift, using motorbikes or cycles to get to work or avoiding the area altogether. Transport for London (TfL), which administers the scheme, said the overall amount of traffic fell by 21 per cent between 2002 and 2006. The result is that 70,000 fewer vehicles are on the streets every day than before the charge began. Meanwhile, the number of taxis has risen by 13 per cent, bus and coaches by 25 per cent and bicycles by 49 per cent, confirming significant changes to London's transport patterns over the past five years. TfL says the extension of the charging zone to the West has produced a fall in traffic in the area of between ten and 15 per cent.
These results are mixed at best, marking the return of snarl-ups to the capital. TfL blames maintenance work, but there is little doubt that congestion is working its way back into London after a peak drop of up to 30%.