The A508 was an A road linking Antrim to the M2, consisting of three new-build parts.
It began on the A26 Dublin Road, and ran east along the new-build Belmont Road to the A6 Belfast Road, which the A508 then multiplexed with for over half a mile. The road regained its number by heading north on the new-build Ballycraigy Road (now the B518). It TOTSOed at the large roundabout to head east along (the once, and now, B95) Greystone Road (the eastern part of which was new-build to serve the motorway, the rest was originally the B95 and now is again) to Rathbeg Roundabout, junction 6 of the M2.
Later on, Belmont Road became part of a rerouted A6, allowing that road to avoid the town centre. The remainder of the A508 was downgraded to Class II status: Ballycraigy Road became the B518 and Greystone Road the B95; this was the original number of that road before the motorway was built and the A508 came into being.