A section of the A379 in the South Hams is on the verge of collapse – and no one knows when it will completely reopen.
The road was partially shut near Modbury after cracks appeared in June, sparking an investigation into its stability.
A Devon County Council spokesman said: “The safety of the public is our priority and we’ve had to install temporary traffic lights on this section of the A379 as a precautionary measure because the road is subsiding.
“We’re currently investigating the stability of the bank.”
A report into the road’s safety will take at least six weeks, and there is no indication of when it will fully reopen.
In the meantime, the council said the traffic lights would remain in place for public safety.
The temporary safety measure reduces the volume of traffic passing through the subsiding section of road at a given moment.