Roadworks on the junction outside North Devon District Hospital (NDDH) are due to start on Monday 13 February.
Devon County Council is converting the current signal-controlled junction into a roundabout. These works will continue for 15 weeks.
Iain Roy, director of facilities at the Trust, said: “We have been working closely with Devon County Council and the contractor to minimise the effects of the roadworks on patients, visitors and staff.
“However, the works are likely to cause delays, and we apologise for any inconvenience caused. Whilst the works are carried out, we advise patients and visitors to leave extra time to get to appointments.”
During the course of the work, temporary traffic lights, footpath closures and diversions will be put in place. There will be lane closures at off-peak times and some narrow lanes, but access to existing vehicle routes will be maintained at all times.
As part of the first phase of the scheme, the pedestrian crossing at North Road junction will be closed and a diversion put in place to the existing crossing near the lower pedestrian entrance to NDDH.
The roundabout scheme is expected to be completed around the beginning of June 2017 and is being funded by Devon County Council. The £1.1 million upgrade will help tackle congestion around NDDH and ahead of future developments in the area.
The scheme includes pedestrian and cycle facilities at the junction and on North Road to the south, as well as a new toucan crossing linking Westaway Heights with the lower pedestrian entrance to NDDH.