How is the newer cars are more fragile during an accident but are more safe for the passengers

Question

How is the newer cars are more fragile during an accident but are more safe for the passengers

In: Physics

Answer 1

You could build an incredibly strong car that takes minimal damage in a collision, just uparmor that bad boy like its a tank

Bad news, when you hit something at 60 mph, the meatbags inside will become meatloaf on the dash

Cars aren’t design to preserve themselves, they’re optimized to protect their occupants at the expense of themselves. The difference between a new $40k car having $10k in damage because its robust or being totalled is irrelevant if you don’t have legs anymore so we favor the legs over the reusability of the car.

Keeping people (and other meatbags like pets) safe in a crash is about decelerating slowly. Highway speed is roughly 27 m/s, if you come to a stop in 10 milliseconds you’ll cover 13.5cm and experience 275 Gs. Bad news, 100 Gs for even a short time will generally break your neck. So to get this down to a survivable level, say 50 Gs, you need to decelerate over more time/distance. Seatbelts help with this, they let you decelerate over maybe half a meter and airbags do a good job supporting your head, but if you want a reliably survivable head-on highway impact you need the person to decelerate over 75 cm which means you need the front end to implode to buy you more time and distance

So that’s what it does. The front and the rear of the car both crumple but with a fair amount of force required to greatly extend the time/distance of the impact so the peak force is lower and doesn’t just turn you into mush. The actual passenger compartment is quite strong and rarely will things significantly intrude on it even if the entire front end is basically missing there’s a decent chance some of the doors still work.

While cars have gotten significantly heavier and more expensive with all the safety tech, it really does help. In 1960 fatalities were 5 per 100 Million Vehicle Miles, by 1980 they were down to 3.3, and in 2018 it was just 1.13 fatalities per 100 Million Vehicle Miles.