Work to reinforce the embankment alongside a lay-by on the A38 at Haldon Hill, near Exeter, starts on Monday night - and is set to continue until the end of next month.
The work will involve the temporary closure of the nearside westbound lane from the junction with the A380 to the entrance of Exeter Racecourse.
The work is due to be completed by the end of November.
A temporary 50mph speed limit will be in place throughout the length of the works, for the safety of the workforce and road users.
Although the risk of delays is low, there may be some additional congestion caused as heavy vehicles will be unable to use the nearside lane.
Highways Agency project sponsor, Michael Hiller, said: “The reinforcement work is important, and will make sure the lay-by remains open to the public and ensure its future use.
“We would remind drivers to obey the speed limit for their own safety and that of workers at the site.”