Interestingly, psychological studies show that most of us would indicate that we would help, but when put to the test we would follow the herd. Human primates that behave as sheep.
I remember stopping to help up a man who was drunk and had fallen over, and everyone simply stood and stared at me.
I was on my way to catch a bus, which was stationary, in view of the man, and people on the bus who had seen me help him to stand up stared at me as though I was in some way infectious - which felt far more uncomfortable than simply stopping to help someone who was lying in the street.
//I would stop unless I thought they were on drugs, trying to assist someone on drugs just gets you into trouble//
A couple of months ago I came across someone apparently unconscious with a bag of shopping spread around him and his phone lying at his side. People just walked past him, I waited until there was no one around and called an ambulance. The 999 operator asked me to check if he was breathing etc. I refused on the grounds that I didn't know if he was out of it on drink/drugs and could 'turn' on me. It wasn't my job to ascertain his condition. I waited with him tho to make sure no one robbed him until the ambulance arrived. Turned out he was just plastered.