1. Spend a month in an accident recovery unit, seeing first hand victims of MVAs.
2. Be in a crash. Somehow this would have to be simulated, at a speed that won't cause injury, but will shock. (I was in a simulated 15mph crash at a fair - it HURT!)
On the day I applied for my license, I visited my dad at the hospital and the guy next to him had a smashed face from a car accident. He had been in a car with a friend, who was driving, and his teenage girlfriend, who was pregnant. The girlfriend's baby died and it was considered unlikely that the girl would survive. The driver went mostly unharmed and was understandably very upset.
I swore that day to always remind myself of this before I get into a car. I used to, but now I don't. The impression fades.
I walked out of it unscathed, but was a kid made of rubber. Dare say these days I'd have smashed ribs and so-forth from the same - at the least.