Motorists have slammed a "daft diversion" that means they must travel 50 miles to get around 1,400 yards of roadworks.
The stretch of road in the village of Melbury Abbas, in north Dorset, is scheduled to be closed for five nights, to allow broadband fibre optic cables to be laid.
But drivers are being threatened with a £1,000 fine if they attempt to use the closed-off road.
People who need to travel between Melbury Abbas and Shaftesbury, just three miles north of the village, will have to drive 10 miles south before joining the A350 and going back on themselves.
The diversionary loop will amount to a distance of around 50 miles in total and residents have said it will cause significant delays to their journeys.
The only other alternatives are along the tight bends and country lanes which are impossible for larger vehicles to navigate.
Jenny Weston, a local resident, said it would cause "traffic chaos" surrounding Melbury Abbas as motorists try to avoid the road closure.
She said: "This will probably cause chaos on the lanes and take longer to get to the destination in the process."
One local resident said: "Are locals really going to use this 50-mile diversion? It seems daft to have to drive so far to get to somewhere that is less than a mile away."
Others have claimed it would be "impossible" for lorries to navigate the tight bends along 'Zig Zag Hill', which is the only other route aside from the 50-mile diversion along the A350.
Melbury Abbas has previously been dubbed the 'Village of the Jammed' as HGVs regularly get stuck along the narrow roads with an average of 18 jams a week.
Alan Perry said: "There is no way a lorry with a trailer will be able to navigate around the tight bends on Zig Zag Hill."
Shirley Ball added: "Let's hope no articulated lorries try the Zig Zag option."
A local resident said: "This will mean a great deal of traffic along Zig Zag hill and the A350. It's going to have very big implications."
One man, who wished not to be named, said his daughter kept sheep on the section of road which will be closed.
He said it will be "impossible" for her to reach them by car in the next five days.
"How is she going to get to them?” he asked.
A spokesman for the local Dorset Council said: "Any person who uses or permits the use of a vehicle in contravention of the notice will be liable on summary conviction to a fine not exceeding £1000.
“This is based on standard council policy."
