Mike, you need to bear in mind that we are talking about rural areas here. In parts of Scotland, main A road can be a ‘single track’ road with passing places or no better than B roads in southern England. Others are better – dual or wide 2-way roads. Many of our trunk roads have been de-trunked but remain key main roads. Our B roads fill in the gaps but remain local access (i.e. joining 2 towns) and can have few properties so they are not truely Residential by any use of the term.
My point was that many rural roads had the national speed limit set (60mph) which leads the navigation systems sending unsuspecting motorists down narrow and windy unclassified roads. This side roads are in many cases unsuitable for large/heavy vehicles. I don’t think this is the intention.
Not all roads are created equal.