Last month, I noticed a Panther van had been sitting, with headlights on, for more than 24 hrs, so I knocked on the door. The driver was ok, watching tv in the back, and glad to know that someone cared about his welfare. I'm not sure what I'd have done if he hadn't answered, probably inquired at the fuel desk, but we need to do something, when things just don't look right - that's a basic human obligation, I think.
A related issue: everyone should put in their cell phone an entry for "ICE" (in case of emergency), with the name & number of who should be contacted in case it becomes necessary. This helpful idea is courtesy of a paramedic who found it very frustrating to be unable to notify someone of an emergency involving their loved one. I have put ICE numbers on my cell, and in my wallet, too - hoping they'll never be needed, but feeling better knowing they're there.