I fell asleep at the wheel once, many years ago. Hired mini into a telegraph pole, luckily lowish speed and just the front nearside stoved in and crumpled. Now I always stop and have 5 minutes if I'm tired. On a bike too - some of the euro trips in tremendous heat make me sleepy, so stop for a fag, walk around and leg stretch.
I'll admit to nodding off for a split second on a bike, many years ago due to sheer exhaustion (my own fault too) but, find the idea of being able to get dressed, take a 20 min bike ride AND return safely, all without any memory - almost incomprehensible.
Long ago I was riding north on the A12 somewhere about Marks Tey catching up to a bloke on a Honda Cub. Just as I got up to him he veered sharp left off the road and high up the embankment. The bike bucked along a fair distance and I expected to be picking up the pieces but he held on and got back on the road. Rude awakening but he probably couldn’t do it again fully conscious.