Abbey Barns was listed as a potential site for a motorway service area when the M40 had not long been built. Like most unbuilt services from the 1970s, it was seen as over-provision as the road was originally only 30 miles long and Iver services were planned nearby on the M25. The land is also green belt and part of an area of outstanding natural beauty, which would also count against the plan.
The site is quite small, even by the standards at the time. It includes provision for a link to the local road network.
The completion of the M40 created a few problems because it created a 210 mile motorway route with no services along it. Abbey Barns was never considered (or at least, seriously considered) here, but a nearby site at Tetsworth near J6 was, also on the original section of the road. After this was rejected another site was considered at Oxford at J8a, this eventually opened in 1998, but it still left the southern end of the M40 (and adjoining section of the M25) without services.
The controversial Beaconsfield services opened in 2009, finally closing a gap in services that was created 40 years ago.