Temporary traffic lights have been erected on the A3052 between Sidmouth and Exeter because of a burst water main.
Motorists are being told to expect ‘heavy delays’.
Devon County Council Highways has issued an alert, warning motorists that emergency works are likely to continue over the weekend.
The burst main is located on Sidmouth Road, between Crealy and the Esso garage.
An alert issued on Twitter said: “There will be emergency works starting now and continuing over the weekend, expect heavy delays.”