London's public transport is prepared to convey an additional 20,000 commuters each morning when road congestion charges begin in February, a report to mayor Ken Livingstone will conclude today.
Transport for London, which runs the capital's roads and buses, admits that the £5 a day fee for motorists driving into the city centre will create a "cascade" of peak time passengers.
But, in a detailed analysis, it scorns predictions of chaos, saying the extra buses will be ample to transport the motorists who leave their cars at home.
The "readiness review" will come as a relief to Mr Livingstone, who yesterday again promised to abandon the charges if they proved unworkable within two months of introduction; he was not "one of those idiot politicians" who would claim success against all evidence.
Accepting the first two months would inevitably be "very difficult", the mayor said: "At the end of that two months, if it clearly wasn't working we would know."
In a finding likely to be viewed with scepticism by critics on the Greater London assembly, Transport for London predicts that the majority of motorists who left their cars would take the bus instead.
It forecasts that congestion charging will lead to 14,000 more bus passengers each morning, while 5,000 people are likely to board overcrowded tubes and trains - representing fewer than one extra passenger per carriage.
While road traffic in central London is predicted to fall by 10% to 15%, the authority believes demand for public transport will rise by 1%-2%.
It intends to lay on 11,000 additional spaces on buses by February to cope with the increased demand.
Congestion charging will be supported by advertising urging people to take the bus.
Mr Livingstone has increased bus capacity by 6%, but has been able to do little with trains and tubes - most of which are operating at maximum line capacity.
Congestion charging is due to start on February 17. It will be policed by more than 100 cameras at city centre junctions that will record registration plates and check against a list of vehicles that have paid.
Roger Evans, the Conservative transport spokesman on the assembly, yesterday cast doubt on the viability of the technology, warning that if even one digit was incorrectly recorded, bills could be sent to "people in Scotland who haven't used their cars for 20 years".
He believed many motorists would ignore warnings of overcrowding and opt for trains: "If you stop someone commuting by car from Essex, they're not going to get the bus. Drivers, frankly, tend to be happier to transfer to trains than buses."
Mr Livingstone adopted a cautious approach yesterday, insisting he was prepared to "pull" the £200m scheme if necessary: "By the end of the Easter break, if it wasn't working by then, I think we would see it as having failed."
The admission was variously interpreted as a lowering of expectations amid unforeseen problems, or a tactical sop to the project's many critics.
However, to the frustration of Conservative critics on the assembly, Mr Livingstone stopped short of declaring the criteria by which the scheme would be judged.
The project is forecast to raise an extra £130m a year for public transport initiatives, by charging drivers to enter central London between 7am and 6.30pm on weekdays. Opponents have raised concerns, including the prospect of traffic gridlock on the outskirts of the charging zone, and the inadequacy of the computerised system intended to log all vehicles entering the zone.
Mr Livingstone said that progress on the technology was broadly on schedule, against his own expectations.
But he said that, even if the scheme passed the two month test, it would take another four months of adjusting and "finessing" of hundreds of traffic lights before it bedded down.