Grade separation was achieved at the A1/A66 junction at Scotch Corner in 1971 by the provision of a two level interchange including two bridges over the A1. The scheme extending to some 1.34m included dual carriageways and was designed "in-house".

Construction was undertaken by Contractors Messrs Brims and Co. of Newcastle.

Although the county boundaries had changed after the re-organisation of local government in 1974 the work on the A1 continued under the direction of the North Eastern Road Construction Unit. The administration of the old West Riding, north of Wetherby was now within the new North Yorkshire County Council.

The County Council as Agent Authority for the Department of the Environment was responsible for the A1(M) Motorway from north of Scotch of Corner to its junction with the Darlington - Bishop Auckland Road A68 in County Durham and also the A66(M) Motorway leading to Darlington.

Further changes were to come about with the demise of the Road Construction Units in 1981 and the increasing involvement of Consulting Engineers by the Department in the design and supervision of major schemes. The Baldersby, Dishforth and Gatenby Lane Junction schemes, referred to later were the first to be undertaken on Trunk Road A1 in the North Riding by consultants. The County did however undertake the Junction improvements at each end of the Catterick By-Pass. Further alterations were made to the Trunk Road when it became the northern limit of motorway construction in North Yorkshire in the mid 90's.