The 176-year-old railway bridge across Abbey Street in Bermondsey is to be refurbished in a £375,000 project backed by Southwark Council and the Railway Heritage Trust.
Last week Bermondsey Community Council gave its clear endorsement to a proposal to release £225,000 of section 106 money from developments at Bermondsey Spa for a scheme to improve the run-down bridge.
"This tunnel is dirty, dank and not a pleasant pedestrian and cyclist route at all," project officer Jillian Houghton told councillors on Monday night.
Subject to the agreement of Southwark's main planning committee, the £225,000 will be added to a £150,000 grant from the Railway Heritage Trust to enable the bridge to be cleaned and painted.
New lighting is also planned and pigeon-proof netting will be installed.
"I'm hugely supportive of this," said Grange ward councillor Mark Gettleson. He also asked officers to see what could be done to improve the "peculiarly revolting" tunnel at nearby Dockley Road.
The central portion of the Abbey Street bridge is one of only two surviving bridges from London's first passenger railway line, the London and Greenwich Railway, which opened in 1836.
The grade II listed structure was designed by Colonel Landmann and features 24 cast-iron doric columns. The other surviving bridge in Spa Road has recently been refurbished.