People travelling to and from Derriford along the A386 Tavistock Road are warned to expect delays heading into the evening rush hour.
Signals on the Looseleigh Lane, Brest Road and Tavistock Road (northbound) approaches to Derriford Roundabout are out due to a damaged cable.
This is likely to cause congestion during peak travel times and drivers are asked to avoid the area if possible.
Pedestrians are asked to take extra care as the problem is also affecting crossings.
We are working to resolve the issue as quickly as possible.