For many years the M22 was just the Randalstown Bypass, and a remnant of Northern Ireland's short-lived motorway plans. Now it's the start of a whole new expressway to the north west of the province.
The M22 is a direct continuation west from the end of the Northern Ireland M2's southern half. It's a decidedly confusing road, and you could be forgiven for thinking you were on the M2. Its number and route make sense in the context of Northern Ireland's original motorway proposals, but make no sense whatsoever in the context of the motorways that were actually built.
It serves as a bypass of Randalstown before returning traffic to the A6 towards Derry/Londonderry. For most of its history, it petered out there at a remarkably unimpressive terminus - a flat T-junction with right turns across the road, beyond which lay the single carriageway A6. Today, though, the A6 leading on from Randalstown to Castledawson has been vastly upgraded, the first stage of plans to provide a continuous fast dual carriageway all the way to Derry/Londonderry. The expressway will be almost motorway standard, but won't actually be an extension of the M22.
The route's interface with the M2 might be the most interesting feature about it - it's certainly the most bewildering. The M22 doesn't take over where you'd expect, which is the A26 junction where traffic wishing to continue following the M2 would turn off towards Ballymena. That point is actually M22 junction 1, and the M22 has already begun. In fact, the transition between the two motorways is at a point where no junction exists - a place about half a mile east of M22 junction 1, where there is, even now, a gap between the carriageways, leaving room for the interchange where the M2 would have branched off northwards to Ballymena.
There have been suggestions that it would now make more sense to renumber the M22 as the main M2, and call the orphaned Ballymena Bypass M26 instead, but so far the Northern Ireland Roads Service has not showed any inclination to change the longstanding, but undoubtedly confusing, status quo.