People travelling to and from Derriford along the A386 Tavistock Road are warned to expect delays heading into the evening rush hour.
A number of the signals on Derriford Roundabout are currently not working.
This is likely to cause congestion and drivers are asked to avoid the area if possible.
The problem is also affecting the pedestrian crossing just north of the roundabout and pedestrians are asked to take extra care or use alternative crossings.
We are working with our contractor to resolve the issue as a matter of urgency.