Kislingbury Valley Way was a planned dual carriageway passing to the south of Northampton town centre. It would have been the ultimate route of the A45.
When Northampton was designated a new town in the 1960s a road network was planned to cope with future traffic demands. As with most projects of this scale it was to be built in stages. For the south of the town there would have been two new main routes. One of these consists of Upton Way, Danes Camp Way and Mere Way and would be used to distribute traffic originating in the town. The other route is Kislingbury Valley Way which would cater for long distance traffic passing through the town. The former was programmed for construction first and would assume the A45 number as a temporary measure. Kislingbury Valley Way would be built later and would take the A45 number leaving the earlier route to function as its intended role as a local distributor.
Road building in new towns rarely goes to plan. Upton Way, Danes Camp Way and Mere Way were built and took the A45 number but Kislingbury Valley Way was scrapped. It is believed plans to built the latter were already abandoned by the time the former was built. This led to changes at Barnes Meadow Interchange where the planned flyover intended to connect with Kislingbury Valley Way was built facing south instead and is on a noticeable curve.