Concrete bollards have been installed to enforce a 45-week road closure after motorists “removed barriers” to avoid detours of up to 28 miles (45km).
Farthing Drove, in Lakenheath, Suffolk, was closed due to a damaged culvert that was undermining the road.
Suffolk County Council put up plastic barriers as work began on Tuesday, but has had to add immovable ones.
Resident Laura Murfitt said “When [the council] shut the road we then have to take a 28-mile detour.”
The council said only the thickness of the surface was currently holding up the road but there was a three metre (10ft) wide cavity under the surface.
A council spokeswoman said concrete bollards have been put on the road “due to members of the public removing the barriers and continuing to drive along the damaged part of the road”.
Ms Murfitt said Farthing Drove was “the main road from Ely and Littleport [in Cambridgeshire] to Lakenheath village, Brandon and Thetford”.
“It has been shut for one reason or another more than once a year for four years and the council never do it up properly,” she said.
The local authority’s official diversion route is 27 miles (43 km) from one end of the one-and-half mile (2.4 km) stretch of road to the other.
“We are working on designs for the reconstruction of the embankment and culvert and are liaising with specialist contractors to ensure the repairs are completed as quickly as possible,” the spokeswoman added.