Maybe a street sign too close to the road combined with the driver’s head too far out the window?
I remember reading a story a few years back about two guys driving home drunk from the bar.
The passenger was puking out the window when the car ran right beside a telephone pole guide wire and loppped the guy’s head off.
The driver continued home and even left the body in the car as he went inside and slept. Some neighbors noticed the body in the car the next morning.
For a tow truck, the wide mirrors should prevent such an occurrence, IMO.