Originally announced in 1964, the M5 was planned to follow the route of the B90 to Carrickfergus. Under the plans it would also have been the southern terminus of the unbuilt M6 Motorway to Larne. The scale of the scheme was reduced to its present form in the 1969 transport review, but it was recommended that the line of the originally planned route should be protected from development. Opening to traffic on 12 September 1980, the M5 was the only one of Northern Ireland's original motorway schemes to proceed after the cancellation of all the existing motorway plans in 1975 following the deterioration of civil order. The M3 later opened in 1995, and had the same number as the original planned motorway in east Belfast, but was a completely different project.