Also, wear your seatbelt.

Source: me, 10y as a FF/Medic

Internal decapitation happens quite a bit.

I think there is something with the individual, however. I have been in all kinds of accidents and walked away from them. Like I can take a beating pretty good.

Delta V

I've worked with a Fireman trained in extraction from accidents. The reality is, most people wind up under the dashboard jammed against the brake pedal. You get folded up under there because we don't require the use of a submarine (crotch) belt. Note carefully, almost all racing organizations require it.

So, on impact, you start leaning forward, the air bag deploys, hopefully you are restrained from hitting the wheel and collapsing it into the dashboard. If forces are high enough, tho, your pelvis is dragged out from under the lap belt by your legs, which bend at the knees driving them up under and behind the dash into the A/C ducts etc. This pulls your hips down to the floor while it's rising up from the engine raising it as it moves back and downward, straightening the path for the rest of you. Your head winds up looking up at the brake pedal while the rest is folded up under the dash multiple times.

Hence the Jaws of Live to separate the firewall from the floor pan to pull you out, unfolding you.

In the process, numerous broken bones in close proximity to blood vessels are slicing you up, damage to your skull has created exit wounds for insanguination, and if you are still conscious, you might realize there is no way rescue personnel will get there in time. Unless you actually hit an ambulance pulling out of the station. If a gunshot wound can cause you to bleed out in less than three minutes, response times of 15-25 aren't really going to do any good.

Your dead, Jim.

Absent a full roll cage and submarine belt, you won't survive a collision at 70. That's often a combined speed of 140 with another vehicle. Humans are not capable of surviving falling 34 feet, which is all it takes to achieve free fall, and it's the stop that causes the damage. About 95 - 118 mph, but there are those who deliberately achieved breaking the sound barrier. With a car body around you - don't forget, that mass can't decelerate faster than you, it drags you with it - we get some minimal protection, but if you plan to survive, then avoidance is your primary tactic.

Go surf interior cams of drivers in collisions and how people bounce around and flip right out of the cab with no seatbelt. Window up, too.

I was in a wreck from a blowout at hiway speed.  We did a 180, slid across 3 lanes of traffic and sheared off the I beam post that said “Welcome to Jones Beach”.  The I beam was turned into an inclined ramp which tossed us like evil knevil into a barrel roll.  We came to rest after 3 or 4 revolutions on the driver side door.  Lucky to survive that one for sure - I got busted up tho.

Craniums (heads) are heavy and upon rapid sudden deceleration its very easy to disconnect your spine from your brain....

With seatbelts?

Cabin intrusion and GeForce.   An example of g's, Dale earnhardt. He died from the head whip.

The Clintons

Plus other things flying around or impacting them. Bleeding from getting cut or crushed by some other object is a problem if you don't get very rapid care. But mostly, the human body isn't meant to go from 65 to 0 or get bounced all over in the space of seconds. Even if everything goes well you're likely to have a massive bruise from the belt and a lot of sore muscles. Heads hitting side windows in side on impacts are a biggie. We may laugh about having a dozen air bags go off for a fender bender, but in a real crash those side bags are a huge help.

Mostly though, from what I've seen and read about, it's people doing stupid stuff that get hurt the most. Not wearing the belt properly. Laying down in the back seat. Legs not where they belong...

Shock..

We all die of shock.

Aortic tears. At scene or soon after.
I've seen 'em come in talking then, "see ya". DRT.
Big tube filled with blood doesn't like to me yanked around.

Inertia don't be like it is, but it do.

I can't tell you how many Gs it is but an instantaneous change of velocity of 18 mph is all the speed needed to generate it.  We are amazingly resilient, fragile creatures.

Yeah that might be a bit conservative...
OP, as explained to me by the doctors...most accidents are survivable under 45-50 mph...most not all, once you go over that speed the damage skyrockets due to the amount of G-force involved..In my case going from 60 mph to zero mph in less than 4 feet..I will deal with it for the rest of my life.....

Tied with the Clintons.

The sudden stop

This.

Brain coupe & counter-coupe (brain bouncing back and forth inside your skull).

The answer is similar to what kills a person who falls off a tall building.  It's not the fall, it's the sudden stop.

internal organs literally rip loose from blood vessels that feed them, while they might not actually break many bones, their aorta has separated from their heart. your BMW CRUNCHING actually helped you a lot in your wreck, that crunching ate up energy that oculd hav ebeen deposited in much squishier mushier YOU.  Old cars could drive away from wrecks that killed passengers, people walk away from wrecks that DESTYROY their cars. many cars nowdays have engine drop features that ditch the engine and make the entire hood area into a crumple zone, makes them destroyed in a wreck, but people walk away form said wreck.

Sudden deceleration at the end coupled with high velocity impact (outside and inside).   Organs are still going at however fast even though your outer body stops.

Head injuries.

Blood loss.

Head injuries mostly though.

This.  Air bags are effective because they reduce the rate of deceleration.

Saw that once at a wreck. No external injuries, signed refusal, ambulance cancelled and boom. DRT just like that.

I lucked out, fire truck was right behind me, I could hear the "Is he dead?" In their voices when they called out my name. I told them to cut me the fuck out of the truck and they obliged. Pulled me out, set me on the ground next to my truck and then rolled on the accident we were originally responding too.

Crumple zones aren't about preventing the kinetic energy of the car from being transferred into the occupants.  The old indestructible cars that could be driven away after a fatal accident were great at doing that. What a crumple zone does is increase the distance and time over which the kinetic energy of your body is dissapated. It's like the difference between jumping off a building onto one of those giant air bags, or onto concrete.  In both cases, the kinetic energy dissapated by your body is the same, but the acceleration and peak forces get higher when you decrease the stopping distance. When your body hits a a solid immovable object like a concrete sidewalk, the only stopping distance you get is how far your flesh and bones distort while dissapating that energy.

A high speed car wreck is about the only thing in this world I'm afraid of. Its just an ugly, violent way to die and you can't predict when the fucking morons surrounding you on the road are going to try to kill you. I especially hate oncoming traffic on 2 lane roads. Long before I was born, my mother boyfriend was killed by a driver crossing the center line. He was/they were 18.

These guys:

Still amazed at Dale Earnhardt's death. Video didn't look like a severe crash.

Or like my Dad used to say. "It's not the fall that kills you. It's the sudden stop at the bottom...."

What kills?

The law that prohibits two objects from concurrently occupying one physical space at the same time.

Pretty much covers it. Just think of it this way. Anything that can hurt you or kill you can happen. As stated above.

In your situation, I'd guess the sudden deceleration/stop and jerk had something to do with your back injury.

I've seen just about everything. Up to decapitation of people. To a brain being thrown infront of the car and then the car run over the brain. It looked as if the head had been put in a helicopter prop.

It's funny though. I've seen accidents you'd swear no one could have possibly have survived. Yet they walk away.

Others with hardly any damage and they died.

Pretty much everything stated here. It's not one single thing that kills.

But most deaths resulted from people not wearing seat belts. Including my own brothers. He was ejected through windshield and his truck flipped over ontop of him from his chest down.

It was muliple things that killed him. Not wearing seat belt, ejection, blunt force trauma (which includes trauma to organs) from going through windshield and hitting the road then crush injuries.

Worst day of my life and still is. He was my only brother.

Inertia is a bitch.

Stuff inside the human body is not designed to change directions in milliseconds, even if the distances travelled aren’t very far. Shit tears, shit breaks. That’s bad.

The amount of force involved in a car wreck is ridiculous.

Back in the early 90's I was at a one car overturn on a curvy 30 mph road. Roads were dry. Drunk kid somehow flipped the Isuzu Trooper onto its side trapping one of his friends underneath the driver side with only the lower half of his body sticking out. It looked like the Wicked Witch from the Wizard of Oz. Driver was arrested for DWI.

Another one same timeframe on a east/west 55 mph road with traffic lights. The north/south road was a 30 mph road.This one occurred at a traffic light intersection. The westbound car got T-boned by the other car who ran a red light. Female in the westbound car was ejected. Didn't appear like she had any major injuries. She died because she landed facedown in a puddle.

Needless to say neither one was wearing a seatbelt.

Lack of brains

No, he did not. He died because his chin impacted the steering wheel. Because the jaw is an arch, force is transmitted to the base of the arch, which is where the jaw articulates with the skull (the TMJ). Fracture lines follow the line of force, i.e., from TMJ to TMJ. This results in a transverse basilar skull fracture.
Transverse basilar fractures do not result from simple decelerative forces ("head whip"). Decelerative forces do cause atlanto-occipital disarticulation, commonly called "internal decapitation". The fact that some non-forensic "expert" with a built-in bias ($) reviewed a perfectly clear autopsy report and came to an incorrect conclusion because of ignorance or an agenda doesn't make it so. Those of us who do this for a living (especially those with aerospace pathology backgrounds, like the forensic pathologist who actually did Earnhardt's autopsy) see these injuries frequently. The mechanism is well-documented and by no means mysterious.

BTW, as to aorta lacerations, the G load required varies somewhat with how healthy said aorta is. The numbers come from correlation with military aircraft mishaps. For relatively young, healthy males (i.e., military pilots), we start to see transverse lacerations at about 50G, and transections at 80G. Where the aorta tears is almost always at the downward part of the arch. That's an anatomically weak area, coupled with it being where the rest of the aorta is attached to the spine. Inertia during the collision causes the big heavy heart to pull on the flexible hose, and it tears at that site.

Watch a few of these. https://www.youtube.com/results?search_query=dashcam+video+of+drivers+in+crashes

No, not hot. You have to want to see them.

This is what I love about this website.  There's always at least one person here that's done it for real or is an SME.

The sudden stop.

Metal meets meat at high velocity

Blunt force trauma damage to vital organs and shock

You are much better off being in a car made after the 2012 safety upgrades.  Also, good European cars seem to be better in crashes at stopping passenger compartment inclusions.  Also, that little econo-box, like a Honda Fit, isn't worth a shit when you get hit by a Suburban.

This is a great video of crashes and what happens inside.

https://www.youtube.com/watch?v=YRh3_ykQioQ

The one at 3:23 is a great one.  Three pax, two belted in.  Third pax becomes a missile.

8:07 is another one.  Wear your seatbelts people!

Actually UI drivers are only involved in 20% of auto fatalities.  NHTSB says.  More than 80% of fatal collisions are caused by sober drivers.  It just doesn’t make the news.

Kinetic energy poisoning of one form or another.... the rest is all relative

As stated above by other it’s a combination of things. A seatbelt increases your chance of survival, but the body can only take so much. Internally is where a large amount of the damage is done.

It happens to people falling off of bicycles too. Going head first over the bars and landing on your chest has killed a few pro riders.

The sudden stop

Blunt force trauma, especially to the noggin.  Crush injuries.  Severe bleeding, internal and external.

Don’t drive impaired, wear your seatbelt, slow down and pay attention to the road.  Your phone, food, etc., can wait.