I did it on the Tube once (in my London days) listening to a Bill Bryson book ... started roaring with laughter for what looked like no apparent reason ... no book and my hair was hiding the headphones!
I worked in London and one evening on the train journey home I fell asleep as usual. I dreamt that my daughter was about to drop a glass and shouted out in a very loud voice "Sue, be careful". What an embarrassment - I didn't want to open my eyes as I knew the whole carriage was looking at me
Strange how you remember silly things like this eh! Mind you, it woke all the others up in time for their stations lol.