My experience of Irish roads, albeit quite a few years ago, was that the road on the map might change from a 'proper' bit of tarmac up to the county border before changing to a poorly maintained farm track as only one county considered the road important enough to spend money on..
Often, if there is only one or two houses on the road, they will just tarmac as far as that house and leave the rest of it. Some roads marked on maps are unmetalled.
It's also not uncommon to find farmers have put gates up or even penned sheep on a road even if it is on the maps as a right off way.
Also keep an eye out for lines of baling twine tied across a little used rural road to assist when turning livestock into a field when moving them on the road, especially at milking time.