I always stop or put a hand up to see if they need help, even gone back round a dual carriageway after i saw a lad on l plates broken down, he had someone coming out to him, but did say thanks for stopping. Attended a RTA on the m4 as ive always got a first aid kit on the bike, and had to do a bit before the ambulance arrived, nothing serious, but its always a comfort knowing theres someone about to help.