I think that people generally do it right, because that's what I've observed when traveling with people, and because people execute lane change and merge maneuvers every day and the vast, vast majority of them are safe.
My experience is that I've been in 6 wrecks because of other idiots.
1# failure to yield at greenlight because she was drunk as s***. T-boned my vehicle. Arrested on the scene, and her cop daddy didn't even try to help her this time. Recurrent theme, apparently...
2# Idiot pulled out in middle of a 4-lane disregarding his stop-sign and stopped right in my lane. No way to stop in time, T-boned the guy. Mexican license plates....don't trust anyone in them cars!!! Saw more dumb stuff down there than anywhere else.
3# Failure to drive to conditions, lost control of her SUV and side-swiped my vehicle, then stood between her car, and traffic, on the military crest of an icy bridge waiting for Darwin to claim her, so I told her to get her ass out of the way so she wouldn't get smashed between her SUV. She also caused another wreck as someone slammed on their brakes to avoid her dumb ass leaving the vehicle in the middle of the road/bridge on the military crest. Her church's van picked her up, and she had Direct General Insurance...'nuff said.
4# Impatient guy at a gas station dragged his horse trailer across the front of my mustang because he was so mad that he forgot he had a horse trailer. I was not in the car for this one, it was parked and I was pumping gas. Progressive was his company, and they refused him any coverage due to it being private property. I faxed him 3 estimates, and he cut me a check for the average. Turned out to not be a half bad guy!
5# Kid thought I was going to make a right on red so he just didn't stop and rear-ended my vehicle, because, you know, I yield on red for oncoming traffic that has green/right of way. He paid me $100 and I let him off without a police report. it was just a tap, and I had a spare tail-light at home.
6# Idiot stopped at a green light. I stopped too. Girl behind me just rear-ended me. Idiot at the green-light sped off. Girl was someone I knew ironically, and I offered to let her pay me for the damages before I submitted the insurance claim. She had 2 months to pay me $500. When she failed, she told me "go ahead and file it". I did. Crazy! Gave her the deal of the century.
This is just in the short time I've been driving, and this is JUST driving. Look at obesity rates and a ton of other stats and personal experiences I have and you have all day long. I stand by my observation, and recant on bagging BSM. Anything you can give Joe Mouthbreather that MIGHT help is a damn good thing. I have been wrong in this thread about that.