Is a controlled stop after a collision from behind easier going slow or fast?

A few years ago a young lady was texting when she came up on stopped traffic. The truck driver she hit noticed her in the mirror, and released his brakes. He moved 25 feet when she hit him. Those 25 feet absorbed some of the energy, and surprisingly, she survived.

Or how about that pile up on I65 in Alabama that knocked the guy in the video out of his seat? I'm not saying he should have been moving faster, but had he been travelling faster, the impact would have been smaller. Simple physics.

 

If I am going to be rear ended I want to be going at least 100 mph. That will reduce the force of impact.

 

And the likelihood of it happening too!

 

Right, the other thing to consider with passenger vehicles is that they'll be hitting that underride bumper lower down on a trailer. Those are only rated up to 35 mph impact resistance while stopped, and beyond this they'd be taking out an axle. That's about 35 vs 70 mph around here, so 45 should keep it intact (some are only rated for 30). Keeping the thing upright without an axle would be more difficult of course. I've had single vehicles flying up behind me faster than that, and I moved left before they got too close. I think that's reasonable when another vehicle is vastly exceeding the speed limit in my assigned lane.

 

I've kinda done both.. neither time did it make the truck go "out of control", but I guess its possible. I got hit by a drunk (pick up truck) driver in Oregon on I-5.. he was doing about 85 and hit me, I was climbing out of Grants Pass and was doing about 35.. I barely felt anything.. just a bump. Then there was a low speed rear ender where a tractor trailer (Cab over GMC for Crecent Lines) ran into the back of the container I was hauling.. it knocked the living **** out of me.. Really bad lerch.. but it was stop and go traffic.. I was stopped and he apparently was going. He hit me so hard it broke his fifth wheel.. No damage to my vehicle or equipment..

 

That's funny, on the one hand you're saying that nothing can be known, and on the other hand you're presuming that I'm talking about you. Why? Because you knew that your intentions were to make this personal.

Well those aren't my intentions, and I think the equipment is at least as predictable as what it's rated for. Something else I know about most everyone (including truckers), who will aimlessly drive around my truck, is what they are not thinking. They are not thinking about avoiding it at a safe distance. So, when all they practice is getting too close at higher speed, chances are in favor of one running into it at some point. That's why I was looking into this, and now I have a better idea of what to expect if it comes up.

 

True enough. I should have simply worded it as which accident would have the greater potential for harm, all else being equal.

If 2 cars of equal size and velocity hit each other head on at 60 mph both vehicles would come to a sudden stop, in other words taking their speed from 60 to 0 mph. The same effect would be seen hitting a wall. Now that IS a perfect case scenario and doesn't take into account such things as absorption and crumple zones, deflection, etc. But it does go to show you how wrong many safety and insurance personnel are because I hear many of them say the same thing.

 

Your looking at that wrong.

You have two different forces travelling at 60mph towards each other. That's a closing speed of 120mph.

That impact would be the same as a single vehicle impact at 120 mph with a stationary wall.

One vehicle hitting at a wall at 60mph will have a less of an impact due to the slower impact speed.

That's just basic math. Not even looking at the physics involved of two vehicles of (x weight) + (y weight) x (x speed) + (y speed) = force of impact

I know which one has more chance of survival and it isn't the two vehicles against each other....

 

Mythbusters debunked that years ago, and you're wrong.

 

Well there you go i hadn't seen that before. I stand corrected but

I still know which scenario i would prefer....