A total of 24 traffic signalling lights in Washington will be out of action for up to eight weeks after a control panel was wrecked by yobs.
The lights are at the junction of the A1231 Sunderland Highway with the A182 Washington Highway.
More than 38,000 vehicles cross the junction every day and Sunderland City Council is reminding all drivers to now take extra care and how there could be delays at peak hours.
Lights at the junction began failing in the early hours of Monday, October 10.
Highways staff inspecting the junction found that vandals had broken into a roadside control box and burnt out its circuit box.
Damage is estimated at more than £20,000 and a new bespoke set of circuits now has to be made and installed.
Councillor Michael Mordey, the city council’s portfolio holder for city services, said: “This is very serious.
“It is not big, it is not funny, and it is putting lives at risk by tampering and destroying traffic signalling.
“Signals were put into the junction to help make it safer. The lights have helped reduce the number of collisions and the council is now reminding all road users to now take extra care and caution.”
There are now fewer than four personal injury accidents annually at the junction but before it was signalised it had been an average of eight a year.
Coun Mordey added: “With the pressure that is now on council resources, this mindless and wanton vandalism places an unnecessary burden on council staff and is a distraction from other tasks.”
The vandalism has been reported to Northumbria Police and CCTV coverage is being studied.
The council has also reported several further incidents of vandalism and anti-social behaviour that have affected the Lumley Close (under A182) subway next to the Galleries and nearby street lighting.
Councillor Linda Williams, chairman of the Washington Area Committee and a Washington Central Ward member, said: “All vandalism needs to be condemned and stopped.
“What is appalling about this incident with the lights is how it is putting lives at risk as the lights were put there for a purpose.
“If anyone has any information about any of these matters they should speak to the police or to their ward councillors.”
There are more than 150 traffic signals at junctions and crossings in Sunderland.