Its always amazed me how some people have the ability to forget these type if things. Major credit given to the emergency services crews who witness this daily.
I witnessed a motorcycle hit a John Deer tractor head-on while going round a bend on a country road at fairly high speed. There was little left to look at after it happened. I witnessed that about 7 or 8 years ago when I was roughly 14 yr old. For the rest of my life, I'm pretty certain that image will never ever leave my memory. It's probably the single reason I've never sat my bike test.