Tesla head on collision with a Honda

[smorgasbord]

Happened to my brother. It's true, he was tailgating and someone brake-checked him.

http://www.all-about-car-accidents.com/resources/auto-accident/fault-car-accidents/fault-rear-end-collision-when-front-car-fault

The "Assured Clear Distance Ahead" Rule
Most of us have heard that the tailing driver is to blame for any rear-end accident. In large part, this is due to the assured clear distance ahead (ACDA) rule, which requires that a driver generally maintain an assured clear distance between his vehicle and anything in front of him.

How does the ACDA rule apply? Let’s say you’re following another motorist on the highway, and you’re both driving at the speed limit, when the driver in front of you stops suddenly. You stand on your brakes, but you still hit the car in front of you. That’s a violation of the ACDA rule. Or, say you’re driving around a corner, there’s a disabled vehicle in the road, and you can’t stop in time before you hit the car. That’s another violation of the ACDA rule. That rule requires you to keep enough distance between your car and other vehicles so that you can avoid hitting them if they stop, or to be travelling at a speed where you can stop if you come upon a stationary object in the road.

 

[Mike_Schlechter]

You are right. It's not new. But it is relevant. Someone noted the S driver was not seriously injured and congratulated Tesla
for their safety design. I just noted that a big part of the safety is weight. The more than 2x greater weight means that
(to first order) the acceleration on impact for the S driver will be less than twice that of the Accord. Or to put it another way,
the heavier S caused the Accord to accelerate more than twice as much as it would have if it had say hit another Accord. Extra vehicle
weight is a zero sum game - it helps one party and hurts the other. This is relevant because as drivers of a heavy vehicle we should
think about this every time we might feel the urge to do something reckless. Someone else may very well end up paying the price.

I'm not sure the physics described are correct. At least when talking about the kinematics of trauma in a motor vehicle collisions from an injury stand point the calculation is (mass x velocity^2)/2. This means that while mass is a factor, it is velocity which plays the largest (exponentially!) role in the transfer of energy. At the most basic level it is energy transfer that causes injury (cavitation, rotations, etc.).

That said, when we are looking at a crash with as much energy as this one clearly had, it doesn't come down to a single factor. I've not read this whole thread, but if the Tesla driver was indeed racing and in their exuberance killed two people I'm just appalled. I've sadly dealt with too many racing related deaths and major traumas. If you really need to go that fast, go to a track, which is controlled and much safer for you and those around you.

By the way, think about that calculation the next time you gun it. Speed kills. Simple as that.

 

[jkirkebo]

You are right. It's not new. But it is relevant. Someone noted the S driver was not seriously injured and congratulated Tesla
for their safety design. I just noted that a big part of the safety is weight. The more than 2x greater weight means that
(to first order) the acceleration on impact for the S driver will be less than twice that of the Accord. Or to put it another way,
the heavier S caused the Accord to accelerate more than twice as much as it would have if it had say hit another Accord.

More than 2x the weight? I though the Model S was ~4700 lbs and the Accord ~2800 lbs. THat's two thirds more, not >2x. Still substantial though.

 

[montgom626]

More than 2x the weight? I though the Model S was ~4700 lbs and the Accord ~2800 lbs. THat's two thirds more, not >2x. Still substantial though.

3554 lbs Honda Accord weight
4,647 lbs Tesla Model S weight

 

[Lloyd]

93 was 2,773 lbs

http://en.wikipedia.org/wiki/Honda_Accord

 

[Jeff Miller]

I'm not sure the physics described are correct. At least when talking about the kinematics of trauma in a motor vehicle collisions from an injury stand point the calculation is (mass x velocity^2)/2. This means that while mass is a factor, it is velocity which plays the largest (exponentially!) role in the transfer of energy. At the most basic level it is energy transfer that causes injury (cavitation, rotations, etc.).

That said, when we are looking at a crash with as much energy as this one clearly had, it doesn't come down to a single factor. I've not read this whole thread, but if the Tesla driver was indeed racing and in their exuberance killed two people I'm just appalled. I've sadly dealt with too many racing related deaths and major traumas. If you really need to go that fast, go to a track, which is controlled and much safer for you and those around you.

By the way, think about that calculation the next time you gun it. Speed kills. Simple as that.

I think the physics of vehicle collisions are surprisingly complex because they are inelastic - a lot of the energy is absorbed by
crumpling the car and how this works out depends on the details of the car. I think you are right about the energy being the
main factor in injury. But the energy imparted to the passengers is dependent on the mass ratios of the cars.
Very roughly, the forces are equal and opposite, so the change in momentum of each car is equal and opposite, so
the (change in velocity of car 1) = (mass of car 2)/(mass of car 1) * (change in velocity of car 2). The energy
imparted to the driver ~ (change in velocity of his car)^2. In the case where the lighter car is half as heavy as the
heavy car, the change in velocity of the lighter is 2x the change in the heavier, leading to a factor of 4 for the energy imparted.

 

[montgom626]

93 was 2,773 lbs

http://en.wikipedia.org/wiki/Honda_Accord

It was a 93? I did not know that. They were doomed in a 1993.

 

[ggr]

... the calculation is (mass x velocity^2)/2. This means that while mass is a factor, it is velocity which plays the largest (exponentially!) role in the transfer of energy.

Sorry, mathematician here, I can't let the use of "exponentially" stand. It's quadratically. The velocity would have to be after the "^" for it to be exponential.

 

[anticitizen13.7]

It was a 93? I did not know that. They were doomed in a 1993.

Yeah, we figured out what model it based on the alloy rims. The rest of the car was so crushed that it was otherwise difficult to determine the generation and year of the vehicle:

My Accord tuner buddy had this to say "That 92/93 Accord didn't fare too well in the frontal offset." "that wheel choice only came on 9293 Accord EXs"

So, 92/93 Accords.

That old car would have gotten decimated by anything new, not just MS. As well, in any newer high end car they likely would have survived.

 

[Jeff Miller]

My earlier claim that a collision with another accord would have resulted in an acceleration of the accord that is roughly half (
or 60% using the more accurate accord/S weight ratio) of that that it would be with the S is wrong. It would result in an acceleration is is 3/4 as large, not half (v vs 4/3v). The totally inelastic collision of equal mass cars head on both going the same speed v results in an acceleration proportional to v and an energy imparted to the drivers proportional to v^2. In the case of a car with mass m colliding totally inelastically with a car of mass 2m both going the same speed, the acceleration of the lighter car ~ 4/3 v and the energy imparted ~ 16/9 v^2. The acceleration of the heavier car in this case ~ 2/3v (half that of the lighter car) and the energy imparted of ~ 4/9v^2. So the driver of the lighter car has it 4x worse than the driver of the heavier car all else being equal (as I noted in my previous post), but only 16/9x ~ 2x worse than if he had hit another light car. Still, 2x is bad enough. Agreed though that car safety features are
now much much better than they were twenty years ago.

 

[Todd Burch]

Just something to think about:

It is easy to sit in a chair at a computer and say "why did the driver do this?", or "why didn't the driver do that?"

These sorts of things happen in a split second. While we'd all like to think we'd react correctly, unless you specifically train your mind and reactions on a specific scenario, there is a very decent likelihood that you would react incorrectly when faced with a split-second scenario like this.

Being judgmental is easy. Learning from this story and trying to apply it to our own lives is the hard part.

 

[imherkimer]

I survived a head on collision and though it was 35 years ago, seeing these images brings chills.
The condition of the Honda is unbearable.
Without having any real perspective, I would not comment on why it happened or who is at fault.
But something in the photos on this thread that jumps out at me is how AMAZINGLY well that car, Model S, protected its driver, not only through the primary impact but the apparent secondary impact into the guard rail. From behind, the orientation of the car is still quite balanced and level. From above it is clear there was an enormous impact directly in front of the driver and the offset shock was fully absorbed across the front end leaving the entire cabin structurally intact, and the driver apparently walked away with no serious injury.

I only survived on that cold day in January, because the primary impact was on the other side of the cabin of the brand new 1978 Suburban, which crumpled, and spun, and the hood came back through the windshield, the whole frame twisted while the engine and drive train pushed into the floor, and the front of the cabin was mashed beyond recognition. The other vehicle was a 1975 International Scout. Both big heavy SUV's, and both vehicles were shocking to see afterward. The wreck of that suburban was left sitting in a lot near my home for months after that. Seeing that, I could never understand how we all survived. No one was racing, or drunk, or driving illegally. Just very sudden. It was all over before I could blink my eyes.

Always, always drive with great care, please.

 

[Electric1]

Just something to think about:

It is easy to sit in a chair at a computer and say "why did the driver do this?", or "why didn't the driver do that?"

These sorts of things happen in a split second. While we'd all like to think we'd react correctly, unless you specifically train your mind and reactions on a specific scenario, there is a very decent likelihood that you would react incorrectly when faced with a split-second scenario like this.

Being judgmental is easy. Learning from this story and trying to apply it to our own lives is the hard part.

Todd- Your wisdom and insight are admired and and appreciated. As we read of such tragedies we should consider that
"there but for the grace of God go I."

 

[NigelM]

Mod note: A few of the personal digs went to snippiness.

- - - Updated - - -

Just something to think about:

It is easy to sit in a chair at a computer and say "why did the driver do this?", or "why didn't the driver do that?"
....

Learning from this story and trying to apply it to our own lives is the hard part.

Thanks.

- - - Updated - - -

Now, on a completely hypothetical basis: If driver X was racing and was accused of causing someone's death through reckless driving, could the car logs be subpoenaed as evidence?

 

[SFOTurtle]

Now, on a completely hypothetical basis: If driver X was racing and was accused of causing someone's death through reckless driving, could the car logs be subpoenaed as evidence?

Without a doubt.

 

[vfx]

I'm only checking back to this thread for a official report. Now i'm quickly scanning the chaff for a blue link.

 

[K5ING]

First, I don't know all the facts. Only what I've read and seen in the news reports and what I've seen on Google Earth and Street View. But knowing something of human nature, I'd be willing to bet that the MS owner and the MB owner held an impromptu drag/chicken race. I remember a show or movie several years back where two drivers were doing a drag race towards a one-lane tunnel. Only one car could fit in the tunnel, and first one in won the race. It was a sort of combination drag race and a game of chicken. I'm guessing this was similar. Both cars started racing on the two-lane section, and neither were willing to be second when it changed to a single lane. BOTH drivers should be held accountable if that is the case.

I hope I'm wrong, but right now, that's how I see it. It also means that the driver(s) were totally at fault, and car itself should bear none of the responsibility. It would have happened in any high-powered car.

 

[Johan]

First, I don't know all the facts. Only what I've read and seen in the news reports and what I've seen on Google Earth and Street View. But knowing something of human nature, I'd be willing to bet that the MS owner and the MB owner held an impromptu drag/chicken race. I remember a show or movie several years back where two drivers were doing a drag race towards a one-lane tunnel. Only one car could fit in the tunnel, and first one in won the race. It was a sort of combination drag race and a game of chicken. I'm guessing this was similar. Both cars started racing on the two-lane section, and neither were willing to be second when it changed to a single lane. BOTH drivers should be held accountable if that is the case.

I hope I'm wrong, but right now, that's how I see it. It also means that the driver(s) were totally at fault, and car itself should bear none of the responsibility. It would have happened in any high-powered car.

Dude, enough with the wild speculation. I've seen movies with all kinds of crazy stuff happen but what ever in the world does that have to do with this incident. Face it, none of us know any more than what has been reported in the news, which mind you may be far from the truth. So let's all show some respect and refrain from any more speculation in this thread and await the facts.

 

[jomo25]

Dude, enough with the wild speculation. I've seen movies with all kinds of crazy stuff happen but what ever in the world does that have to do with this incident. Face it, none of us know any more than what has been reported in the news, which mind you may be far from the truth. So let's all show some respect and refrain from any more speculation in this thread and await the facts.

Personally, I think it's fine to speculate. This is a discussion forum. Most of what is posted in the entire forum is just opinions and speculation. If we only stated facts, the forum as a whole would be bare.

That said what i think we should refrain from here are trying to impose opinions as fact or attacking others for their opinions. But that can be said of any thread not just this one.

 

[Johan]

Personally, I think it's fine to speculate. This is a discussion forum. Most of what is posted in the entire forum is just opinions and speculation. If we only stated facts, the forum as a whole would be bare.

That said what i think we should refrain from here are trying to impose opinions as fact or attacking others for their opinions. But that can be said of any thread not just this one.

It's just that speculating about future battery technology, prices of Gen III cars, the next earnings call, how fast can you go in a Model S, when will my car be built etc. etc. is bascially harmless. In this thread we are talking about an accident where two people died. And what I don't like is people starting off their argument like this "First, I don't knoow all the facts" but later in the post "I'd be willing to bet that the MS owner and the MB owner held an improptu drag/chicken race" and then at the end of the post "... that's how I see it. It also means that the driver(s) were totally at fault...". So you've gone from stating you basically do know to in a few sentences being pretty convinced of the correctness of your theory.

What you have there is something dangerous. Think if you are the driver of the Tesla and you didn't race og speed at all, that there is a completely different explanaition for the accident, and then you read these kinds of statements online. I know this forum isn't quite the daily news or whatever, but when things are said sometimes they are very difficult to take back. Think of people who are innocent but for one reason or the other accused of rape, child molestation etc. I know it's not the same but I do know that you will forever be known as "the guy who was accused of rape but got off". What if this driver is cleared in every possible way of any wrong-doing, but there is massive speculation online that leads to speculation in his community etc. etc. all leading to a situation where he will be forever known as "the guy who was racing his new car and killed two people and got away with it". I know it's all just words and "harmless" speculation and what not, but we are talking about a very serious matter. I will not post in the thread again.