In the 1970s, the Northern Ireland section of the Belfast to Dublin road was far better than the Republic of Ireland section.
Much of the route north of the border was already dual carriageway, but the route south of the border was entirely single carriageway.
The first short section of motorway south of the border was not built until the late 1980s and even that was shorter than the Belfast to Lisburn part of the intercity route, which was a motorway as long ago as 1962.
The situation has been reversed to a dramatic extent. The Republic of Ireland completed its motorway to the border in 2007, so has long been far better than the NI sections.
Critics say that Ireland got European money, which it did, but the Irish authorities also introduced a tolling point, which has proved lucrative and has helped fund the route.
The refusal to consider tolls on both the Belfast to Londonderry and Belfast to Newry roads mean that they are still substandard, albeit now being improved.
The A1, from Sprucefield to the border, is now entirely dual carriageway, some of it to a high standard.
But the oldest sections of dual carriageway are now utterly inadequate for such a major route, with deadly gap junctions in which motorists have to wait in the middle before turning right on or off the road, amid fast traffic.
These gaps have been implicated in fatal accidents. They must be closed, yet the plans to do so have taken many years.
An inquiry is to be held into the upgrade plans, which involve some landowners and some small roads losing direct access. Crossing the road will happen at bridges or underpasses, rather than gap junctions.
These are essential reforms, even if they are — regrettably — inconvenient for some local residents.
Safety is key. Traffic coming off a motorway from Dublin suddenly finds itself navigating tractors coming in front of it. This crucial upgrade is long overdue.