Before I started riding, I witnessed a crash where a truck pulled out from a driveway in front of a roadie (with helmet) and the cyclist hit the driver's door broadside at full speed. His head was instantly through the driver's window, and obviously there was severe impact all around as the bike stopped instantly.
He was lucky he hit the window. If he had been one foot further forward or back, he would have struck the door post, and I would guess his injuries would have been more severe.
I will never forget the sound of that impact.