Local residents are being warned that the A36 near Bath will be closed for up to three months by the Highways Agency after a number of cracks were spotted in the road.
The discovery means that some parts of the road could be at risk of sliding down the hill.
The A36 from Bathampton to Brassknocker Hill in Monkton Combe will be closed for necessary remedial work to be carried out.
The road recently had some parts resurfaced, after which a survey of the road discovered the cracks.
The A36 provides one of the main artery routes into and out of the city and the closure will mean thousands of drivers will need to find alternative routes while the road is stabilised.
A Highways Agency spokesman said: “Cracks in the road surface found along this section of the A36 demonstrate evidence of slope instability.
“Work to remedy this will involve installing 14 metre deep concrete piles along a 240 metre long stretch of highway in order to ensure the road is adequately supported.
“The start date for this work has not yet been finalised but it is unlikely to commence before March 2014 and may take up to three months to complete.”
During the work it is expected that traffic will be diverted along the A4 to Chippenham and then travel on the A350 to Warminster. Drivers heading into Bath will be following the route in reverse.
