[squigg]

Remember most of these "major" routes are single track A road at best, apart from our small motorway network. Once you are north of the central belt, where Glasgow and Edinburgh are, your main road can be anything but. This means they don't cover as much ground as you might expect, hence we do need quite a few of them. https://trafficscotland.org/livetrafficcameras/

[tialaramex]

Single Track means there is just one vehicle width shared both directions, if you meet someone coming the opposite way too bad, the next size up is Single Track with Passing Places (at intervals the road is wide enough for vehicles to pass in opposite directions). Not many Single Track A roads left in Britain, the A roads have mostly been upgraded even in Scotland. You're likely thinking of single Carriageway, which means there's only one road surface but it has separate lanes in each direction. Lots of those.