Completed in the 1960s and not changed much since, the Northern Ireland M1 is a mostly two-lane affair that stretches to nearly 40 miles - the longest stretch of road of this standard in the province. For many years it ended at Dungannon, a terminus that never quite seemed right - there's plenty more of the province west of there but the motorway gave up. In 2010 that was finally put right, when the Northern Ireland Roads Service opened another 12 miles of expressway leading onward from the end of the motorway to Ballygawley, a better terminus to serve Fermanagh and Tyrone. Despite this new road being a direct extension of the M1 it's not a motorway and is instead part of the A4.
The M1 has numerous missing junction numbers, intended for the various expansive motorway plans that the Northern Ireland Assembly had, almost none of which saw light of day once Westminster took control again. Among these are two junctions for the M11, which would have started on the M1, headed around the north of Lisburn, and then crossed it again to go south, and one for the M8, intended as a southern bypass of Belfast.
One missing junction is now missing: it's been used for a new junction that wasn't on the original plans. Number 8 was for the M11 to cross, before heading south to the Irish border. It's now been taken up with a new cheap-and-cheerful exit for the A1, with the original (free-flowing) junction half-closed and now used to access a retail park, mostly. This seems to sum up the development of Northern Ireland's motorways.