How could a car crash kill

"Blown up? You told me they died in a car crash."

"A CAR CRASH?!" bellowed Hagrid, making the Dursleys cringe once more. "How could a car crash kill James and Lily Potter?!"

Surprisingly, Uncle Vernon walked towards the giant and pulled down a chart on the wall. Harry looked puzzled as to how it had gotten there, and even the giant looked confused. Vernon took out a rod and began to talk.

"How could a car crash kill James and Lily Potter? Well it's quite simple really. Lets' assume that the speed of impact was sixty miles an hour. At that speed, a metallic shell would crumple, the victims would be crushed by relatively solid objects being pushed in with substantial force, not forgetting the glass of the windscreen suddenly fragmented and thrown in every direction. Even a small shard of glass would cause a deep gash upon hitting a human being, and with so many flying around, gashes are pretty much a certainty. Additionally, the trauma of such a sudden shock would leave, at best, severe bruising, broken bones at worst. Being knocked unconscious is highly likely. And all of this is made worse if the victims were not wearing seatbelts. Escape from the inside of the car would be very difficult, if not impossible, and even if the victims had magic wands, it is very likely such flimsy instruments would snap clean in half, if not more pieces. Reaction times from the instant of impact would be zero. The victim would have no time to perform any kind of spell to alleviate the effects of such a crash."

Harry simply gaped at his uncle. Hagrid seemed lost for words before finally speaking up.

"But surely they wouldn't have been going so fast..."

Uncle Vernon shrugged.

"Even at thirty miles an hour, severe injury is very likely, if not fatality. Thousands of people are killed worldwide in car accidents every year. However proficient James and Lily were in magic, it doesn't exempt them from the laws of physics. A car crash could have easily killed them."

Hagrid blinked owlishly, a look of stunned bewilderment on his face as he quietly spoke a single word.

"...Oh."