A couple days ago I decided to try sketching people in the bus while on the way to the airport. I brought a tiny little book with me and managed to draw four people. The guy (in green) was relatively easy to draw. He was distracted by his ipad and barely moved. The older gentleman (in red) man sitting a couple seats ahead of me was there long enough for me to do his portrait.
It's interesting to see how some people fidget a lot more than others. The unfinished guy on the lower left kept moving his head and looking all over the place, so I only managed to do draw a basic shape. The one on the lower right didn't move much but I lost my view when more people entered the bus.