Confession time - I did ride on an M road a few years ago.
It was when I was riding the D10/1 timetrial course on the Rainford bypass. Now this course used to be my local 10 course in the late 60's, but now living in Kent, it was a rare visit to ride the course again. In the meantime, they had changed the "turn" from a simple 4 exit roundabout, to a huge motorway roundabout, with about 5 exit points. I got confused going round the roundabout and took the 4th exit, which was the motorway, instead of the 5th exit. Took me about a 100 metres to realise, quickly dismounted and walked back to the roundabout.
It was when I was riding the D10/1 timetrial course on the Rainford bypass. Now this course used to be my local 10 course in the late 60's, but now living in Kent, it was a rare visit to ride the course again. In the meantime, they had changed the "turn" from a simple 4 exit roundabout, to a huge motorway roundabout, with about 5 exit points. I got confused going round the roundabout and took the 4th exit, which was the motorway, instead of the 5th exit. Took me about a 100 metres to realise, quickly dismounted and walked back to the roundabout.