I had a great instructor when I did my 5-day intensive bike course. It wasn't all theory and instruction with him, during the lunch breaks he'd talk to us about the many pleasures of biking as well as dangers. He told us about the "biking brother/sisterhood" where you show recognition if not respect to other riders by giving a little nod or wave. Most importantly, he said, when you see another biker parked on the side of the road always assume he/she is in trouble. Stop and find out if they're having a specific problem. Who knows, you might just be able to help, and if you do, think of the kick you're gonna get out of it for the rest of the day. Anyway, he said, what's it gonna cost ya to roll up behind him, ask "you allright, mate?" get the thumbs up from him and you carry on with your ride? 45 seconds?