Joined up tarmac

For reasons explained in the second half of this post, I entered a rabbit-hole about Irish roads and their numbers. Before there were any Motorways in the Republic, there were T for Trunk roads and L for Link roads [as R from my father's AA Road Book of Ireland] and a spider's web of bohereens and back-roads which were known and used only by local inhabitants, so didn't deserve a number. T and L roads were renamed and renumbered in 1977 as N for National roads. Nobody used these numbers! The main road from Dublin to Waterford, Cork & Limerick was the Naas Road. After Naas [30km from Dublin] you had to memorize the list of towns and villages along the way: Kilcullen, Castledermott, Carlow, Leighlinbridge, Paulstown [L for Waterford, R for Kilkenny], Gowran, Dungarvan [not that one, the smaller one], Thomastown, Ballyhale, Mullinavat, Waterford!The British system radiates from London and goes clockwise A1 Edinburgh A2 Dover A3 Portsmouth A4 Cardiff A5 Holyhead A6 Carlisle. Splitting the…