The steep route, which links Thirsk and Helmsley on the edge of the North York Moors National Park, handles around 130,000 vehicles each year. Because of its extreme one-in-four gradient, the road requires regular upkeep to stay safe and operational.
During the closure, North Yorkshire Council highways teams stabilised the rock face, upgraded the drainage network, resurfaced the road, and replaced all road markings.
Engineers overcame an unexpected challenge when they hit natural water springs that serve two local houses. The team quickly modified the design to divert the new drainage system and protect the water supplies.
Cllr Malcolm Taylor, Executive Member for Highways and Transport, said:
The closure allowed our teams to carry out a range of essential maintenance and improvements on this unique section of our road network safely. We would like to thank residents, businesses and motorists for their patience while the work was undertaken. These improvements will help to ensure Sutton Bank remains safe and resilient for all road users.
The council stated that combining these infrastructure improvements into a single planned block minimises disruptions for drivers throughout the rest of the year.