These drawings were done during my commuter rail days. The trick was to do them without staring at people, otherwise they'd find another seat or cover their face with a newspaper. I liked the roughness and spontaneity of having to work fast, and using a black marker forced me to keep the accident as part of the work. It's a combination of spontaneity and accident that brings life to a work.
My book on Train People is available on Blurb.com