Smash the glass video

I knew I'd read something interesting about glass/windshields in Mary Roach's book Stiff: The Curious Lives of Human Cadavers. Here's the relevant passage:

"The dead's first contribution to safe driving was the non-face-gashing windshield. The first Fords came without windshields, which is why you see pictures of early motorists wearing goggles. They weren't trying to affect a dashing World War I flying-ace mien; they were keeping wind and bugs out of their eyes. The first windscreens were made of ordinary window glass, which served to cut the wind and, unfortunately, the driver's face in the even of a crash. Even with the early laminated-glass windshields, which were in use from the 1930s to the mid-1960s, front-seat passengers were walking away from accidents with gruesome, gaping scalp-to-chin lacerations. Heads would hit the windshield, knock out a head-shaped hole in the glass, and, on their violent, bouncing return through that hole, get sliced open on the jagged edges.

Tempered glass, the follow-up innovation, was strong enough to keep heads from smashing through, but the concern then became that striking the stiffer glass would cause brain damage. (The less a material gives, the more damaging the forces of the impact: Think ice rink versus lawn.) Neurologists knew that a concussion from a forehead impact was accompanied by some degree of skull fracture. You can't give a dead man a concussion, but you can check his skull for hairline cracks, and this is what researchers did. At Wayne State, cadavers were leaned forward over a simulated car window and dropped from varying heights (simulating various speeds) so that their foreheads hit the glass. Contrary to popular impression, impact test cadavers were not typically ushered into the front seats of actual running automobiles, driving being one of the other things cadavers don't do well. more often than not, the cadaver was either dropped or it remained still while some sort of controllable impacting device was directed at it.) The study showed that tempered glass, provided it wasn't too thick, was unlikely to create forces strong enough to cause concussion. Windshields today have even more give, enabling the modern-day head to undergo a 30-mph unbelted car crash straight into a wall and come away with little to complain about save a welt and an owner whose driving skills are up there with the average cadaver's."

(Chapter 4, "Dead Man Driving", pp 88-89)