So, is the below a fairly accurate technical account (forget the drama)?

Makes me wonder why I even drive a car . . .

:-) neil
PS: another child just born!
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What are the two collisions that happen in a crash?
1. The impact of the car with the object.
2. The impact of the driver with the inside of the car (concept of the second crash)
If a car leaves the road at 35 mph and hits a large tree, how long does it take to dissipate the kinetic energy contained in the vehicle and everything in it?
It takes about 7/10 of a second.

Concept Of Second Collision
When it looks like you cannot avoid the collision that is about to happen in front of you, you are actually in two collisions.

The first is the car with whatever you hit or whatever hit you.

The second collision is when you are stopped by the windshield or steering column if you do not wear your safety belt. Additionally, any object that is not secured in place will go flying to the front of the car, striking what is in front of those flying objects

What happens in a crash?

Newton’s first law of motion states: A body remains at rest unless a force makes it move. A force is required to change the speed or direction of a moving body. This law means that it will take a force to start and stop an object in motion1.

Below is the 7/10 of a second impact (including people and objects in the vehicle):
1/10 sec. - In the first tenth of a second: the car and everything inside are going at the speed of the vehicle, for the purpose of demonstration we will pick 35 mph. The front bumper strikes the tree and begins to deform. The front center of the car slows to 0 mph; the rest of the car and its occupants continue moving forward at 35 mph.

2/10 sec. - In the second tenth of a second: the bumper continues to deform as the energy of the crash is being dissipated; the radiator and fan begin to crush; the engine and frame strike the tree and begin to decelerate.

3/10 sec. - In the third tenth of a second: the frame and body of the car continue to deform; the passenger compartment, front dash and windshield have decelerated to 20 mph. The car's passengers are still traveling forward at 35 mph.

4/10 sec. - In the fourth tenth of a second: the frame of the car decelerates to 20 mph and continues to dissipate the energy of the crash. The safety belts and passengers continue forward at 35 mph.

5/10 sec. - In the fifth tenth of a second: the safety belts begin to deform by stretching to decelerate the passenger in a comparatively gentle manner. Occupants decelerate to 25 mph, the car frame has decelerated to 15 mph. Unbelted occupants continue forward at 35 mph. Loose objects from the back seat and deck continue forward at 35 mph.

6/10 sec. - The sixth tenth of a second: the safety belts have reached their deformation limits. Belted occupants decelerate to 10 mph, the dashboard and windshield decelerate to 0 mph. The car body, frame and engine continue to absorb the energy from the crash. Unbelted occupants continue forward to strike the dashboard, steering column and windshield at 35 mph. Loose objects from the rear seat and deck come flying forward to strike the front seat passengers at 35 mph. The unsecured objects in the back of the vehicle could strike with enough energy to cause injury or death.

7/10 sec. - In the seventh tenth of a second: the frame and body have finished deforming and rebound in the opposite direction (reaction to the crash action); the belted occupants rebound from the safety belts, their heads continue back to come into contact with the head restraints. Unbelted occupants reach 0 mph by striking the windshield, steering column and dashboard, they deform and crush. Their internal organs, still going 35 mph, strike their rapidly decelerating body frames2.

The crash is essentially over!!! The belted-in occupants count their lucky stars and continue on with their lives. The unbelted occupants are carted off to the hospital or morgue for an extended stay; some longer than others.

Don't forget the impact force of the eight pound crowbar to the neck of the buckled in @ 35MPH.....

EDIT:
Ah, I see it was mentioned there, hitting the rear passengers....

__________________
1983 Mercedes 300SD
1987 Mercedes 300SDL
2001 VW Passat 2.8 AWD
2007 OM642 Jeep WK 4x4

Wow!! That is powerful stuff. Thank you for sharing.

I have three daughters - One 19 who is driving, one 17 who is about to be, one 14 who will be in 3 years.

I will share this with all of them - could save a life.

-g

__________________
GG NJ USA
1983 300SD (Sold at 198K)
1989 560SEL (205k) - slowly restoring
2009 Toyota Camry Hybrid (6k) - daily driver
1995 Colt Vista AWD (145k) - fun car! spare
1991 Buick Riviera 3.8l (85k) - fur die Kinder
RIP: 1965 LeMans/GTO Convertable -my first
RIP: 1968 GTO 400 HO w/ 400HP - ballsy!
(blew the motor racing a '69 GTX - bummer)

They forgot impact #3

Your internal organs smashing against the inside of your body. Namely your brain and the front of your skull.

Sounds like you took this verbatim from some kind of pro-seatbelt propoganda. I got nothing against seatbelts, but propoganda aint always telling you the whole story. Impact #3 is gonna happen whether or not you're belted in. The rosy outcomes and counting your lucky stars aint always gonna happen.

Don't believe everything you read.

PX

__________________
Pxland

2001 Honda Accord

1995 Jeep Cherokee

1973 MB 280SEL 4.5

That article, or some iteration of it, was in Readers Digest, back it the late 60'ds(??). I read as I was learning to drive and have worn my seatbelt 100% ever since.

__________________
KLK, MCSE

1990 500SL

I was always taught to respect my elders.
I don't have to respect too many people anymore.

i was in a really bad wreck and not wearing the seat belts actually saved my life.. the force of that 3in belt on my body would have killed me.

__________________
72 W114/M130

RedMeat cartoon

There is always that one odd chance where the seat belt may actually cause your death. However, these are VERY rare occurances. I owe my life twice over to seat belts.