The new Underground line is crucial to the smooth running of the Dome in the New Year, but transport experts believe that its plummeting reputation will drive thousands of visitors into their cars.
The Jubilee Line Extension was specially designed to take traffic away from south east London, where the roads are already badly clogged. But since it was opened three weeks ago, it has been plagued by delays and cancellations.
Steve Hounsham, spokesman for the environmental pressure group Transport 2000, explains: "It's absolutely essential that London Transport are able to cope with the huge numbers of people using the system. Otherwise there will be a nightmare situation with people trying to get there by car. If word gets around that the system isn't efficient then people will look at other ways to get to the Dome."
The Jubilee Line has repeatedly run into trouble despite using some of the most sophisticated transport technology in the world.
The system is unique because it can "read" information from computers installed across the network. But if it doesn't understand some of that information it turns all signals from green to red. "The computer system is on the sensitive side," admitted a Jubilee Line Extension (JLE) spokeswoman. "If it senses anything irregular, the signals go red, which means the train stops. It's a fail-safe system."
Since the final extension from Waterloo to Green Park opened, an average 225,000 journeys have been made each day on the Jubilee Line. This will rise considerably when the Dome opens for business on 1 January.
Commuters are only too familiar with the hold-ups between stations. David, a computer analyst who has to travel daily to Canary Wharf, isn't impressed. "You're presented with this shiny new railway so you expect it to work," he says.
Gina, a catering manager, is also disappointed by the service. "Somehow it's more frustrating because it all looks so new and modern.They get your hopes up but it's no better than the Northern Line at the moment."
There is very little evidence that the situation will improve by the new year, when thousands more visitors will cram on to the system.
Yesterday, the JLE spokeswoman was recommending alternative ways of getting to the Dome - before it's even opened.
"Nobody said it was going to be perfect from day one," she said. "There are alternative means - Connex are doing a non-stop train from Victoria to Charlton. There are special buses too. And river buses. And if there's signal failure between North Greenwich and Waterloo you can always get the Central Line and go via Stratford."