Transport for London (TfL) has warned it could close Gallows Corner flyover if more government funding is not forthcoming to tackle its funding deficit.
The capital's transport operator published a report outlining service reductions it says it will have to make without further support.
The government has provided more than £4bn to TfL throughout the pandemic, but the latter revealed it is still facing a £1.3 billion funding gap for 2022/23.
London's transport commissioner Andy Byford said the capital would not recover from the pandemic "without a properly funded transport network", adding: "The government must act now to save the recovery.
"A failure to provide stability and certainty for TfL means we are now on the brink of entering a period of the managed decline of transport in London."
A "managed decline" would result in no new investment by TfL in the transport network, meaning many major projects would be scrapped or delayed.
Gallows Corner flyover would be "at risk of closure" in this scenario, which TfL says would be necessary to close its funding gap completely.
If this happens, a TfL spokesperson said: "Our programme of larger renewals of structures and tunnels managed by TfL – such as at Gallows Corner - would need to be reduced, leading to the deferral of some projects.
"These structures therefore could be at risk of closure until funding for their renewal becomes available."
The flyover was first built as a temporary measure more than 50 years ago.
The Recorder reported last month that TfL had investigated multiple design options to replace it and was working on a business case for the Department for Transport that would represent an "asset enhancement".
But TfL's closure threat brought an angry response from Havering Council leader Damian White, who said: “Gallows Corner is a critical junction for London, Essex and beyond.
"For years residents have had to put up with a flyover that’s well past its sell-by-date and a junction that’s gridlocked, dangerous and simply unfit for purpose.
"The council will drive on until Havering gets the funding and investment it deserves.”
A government spokesperson said the emergency funding it has already given TfL showed its commitment to supporting the capital's transport network.
“We will continue to discuss any further funding requirements with TfL and the mayor of London. Any support provided will focus on getting TfL back onto a sustainable financial footing in a way that is fair to taxpayers across the country.”
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