I know we can all get a little cynical at times but the following can show there's still a lot of good folk out there; This reflects my experiences as a taxi driver, most of which are probably unreported. Nice to actually see it in action though.
It happens over here too. Usually the only people that know are the one that helped and the one who was helped. people in general aren't as bad as one is led to believe from watching TV.
When I encounter that situation, many times the assisted person will say they want to give me something. The only thing I will accept is a promise for them to help some future person in the same situation.