Head on collision - choose a tree rather than an oncoming car ?

uberalles

If faced with a car driving towards you is a hitting a tree a better option?

I've heard that a head on crash doubles the speed so is a solid tree a better idea ?

Hopefully I never have to choose but just wondering

Hal Decks

What a ridiculous post!

corktina

you'd never know if you made the right choice.

Mena

Lol

Yeah, oncoming car speed + your speed = speed of the collission, so tree may appear to be a better option, but then there would be hundreds of other factors you'd need to take into account.

phill106

Got to factor in what you are hitting. Is it a sapling or a huge oak tree!
There would be some give in cars, with crumple zones and airbags etc, while trees are meant to just stand there solidly.
Can I not just aim for the ditch?!

Bruthal

Mena wrote: »

Lol

Yeah, oncoming car speed + your speed = speed of the collission, so tree may appear to be a better option, but then there would be hundreds of other factors you'd need to take into account.

Oncoming car at 100kph and you doing 100kph, would probably not be as bad as hitting an immovable object at 200kph in terms of deceleration time. The energy of the impact would be similar probably. So the outcome would be probably equally as bad with the crumpling of the cars.

If you hit an oncoming car that is doing 30kph, and you are doing 100kph, they will be pushed backwards, so again, its probably not the same as hitting something at 90kph which does not budge, the deceleration would probaby be higher hitting a solid tree square on that doesnt move at all.

vicwatson

Poll ?

The Big Red Button

Obviously, the combined speed of two moving cars is far higher than the speed of one moving car and a tree. But, as mentioned, there are many other factors involved.

If it was me, I'd absolutely head for the tree. No hesitation. If you're going to be in a head-on collision, you're going to end up pretty f*cked up either way - why create more casualties? There could be children/babies in the back-seat of the other car - how could you live with yourself knowing that you'd made the choice to crash into that vehicle?

seamus

It's not actually as simple a calculation as above. 100kph + 100kph does not equal hitting a tree at 200kph because the vehicles absorb so much of the energy of the crash. On top of that you're unlikely to hit the other car dead head on, you'll hit eachother at even a slight angle, which reduces the forces involved.
A tree is a scarier prospect because it provides very little give, so most of the force of the crash is transferred to your vehicle. It's circular profile means that hitting it from any angle is a "head on".

For most people I think hitting the tree is most obvious choice because you're only risking your own safety. Go for the other vehicle and you're dragging them into the incident and they could have two kids in the back, etc.

AugustusMinimus

robbie7730 wrote: »

Oncoming car at 100kph and you doing 100kph, would probably not be as bad as hitting an immovable object at 200kph in terms of deceleration time. The energy of the impact would be similar probably. So the outcome would be probably equally as bad.

In that scenario, you'd take hitting the car, as you would have two crumple zones to disipate the energy of the impact. Trees have no crumple zones.

hardCopy

Are we talking about an actual on the spot choice of which one to hit? I don't think I'd want to deliberately hit the car but I'd want nothing to do with a mature tree.

A couple of months back a people carrier hit a tree outside our house, not sure how fast he was going but he managed to mount the kerb, cross a bus stop and hit the tree.

The car was a writeoff, two passengers had to be cut out of the car and all 4 required separate ambulances.

The tree had two very small chips in the bark.

afatbollix

We hate trees in rallying circles. The crashes where most drivers are killed is because they hit trees, They can split a car in two like cheese wire!

corktina

you would be very unlikely to get the chance to decide which to hit. Altthough people often say that an accident seemed to happen in "slow motion" ,in reality, they usually occur before you can react at all

Bruthal

AugustusMinimus wrote: »

In that scenario, you'd take hitting the car, as you would have two crumple zones to disipate the energy of the impact. Trees have no crumple zones.

In terms of reducing impact level, probably. But in reality avoiding hitting another car would be preferable.

Stereomaniac

I can say I'd rather hit the tree, but in the moment, I know it probably wouldn't be like that!

Bruthal

corktina wrote: »

you would be very unlikely to get the chance to decide which to hit. Altthough people often say that an accident seemed to happen in "slow motion" ,in reality, they usually occur before you can react at all

Yes its an unlikely choice to arise, but probably has at some time by some on rare occasions.

I think the slow motion thing is a hindsight thing probably. People can recall every detail of a serious occurrence that only took a couple of seconds to happen.

Bruthal

vicwatson wrote: »

Poll ?

Probably not as bad as a tree...

im invisible

Go for the tree, every time

af_thefragile

https://www.youtube.com/watch?v=XbEU42UGXhE

Yeah...

BrianD3

So many variables involved eg type and age of car, type of tree and diameter of trunk, angle of impact and how much of your car overlaps the tree/other car.

Given the choice between hitting a tree head on or hitting an oncoming HGV head on at double the closing speed I'd pick the tree every time and try to hit it with the centre of the front of the car. If oncoming vehicle is a car it's not as clear cut. One disadvantage of hitting a car is the other driver might make a move which makes the angle unfavourable for you and maybe him as well

The Renault Laguna II was very solid when driven into a big tree at 55 mph impacting with the centre of the front of the car - however the forces on the occupants from the sudden stop may have caused death or serious injury

https://www.youtube.com/watch?v=2fLg8eQaPyE

The much older design Ford Sierra perfomed terribly when driven into a tree like barrier at a similar angle and speed

https://www.youtube.com/watch?v=zg9aHJl8MR8

The IIHS have recently started doing small overlap crash tests at 40 mph, if you hit a big tree with this overlap and speed the results would probably be reasoanly similar. The Lexus IS did badly in this test, your legs would be smashed and you'd be trapped in the car.

https://www.youtube.com/watch?v=wnK-TovPgrc

peasant

Depends on whose fault it is that I suddenly find myself faced with an oncoming car:

- if it's mine I'd try for the tree
- if it isn't I'd take my chances with the crumple zones (especially as my van would most likely hump the oncoming car)

harsh, but true

ZETOR_IS_BETTER

Mythbusters answered the question with regards impact speed and force on a car in a head on collision and hitting a wall head on

Basically makes no difference

CiniO

Hal Decks wrote: »

What a ridiculous post!

That's not ridiculous post. That's actualy very wise question, as everyone might be forced to make that kind of choice some day and it's better to know what to choose.

CiniO

If 2 cars each at 50km/h crash head on, assuming they are the same kind of cars (the same crumple zones, the same weight, etc) it will be equal effect as each of them hitting the wall at 50km/h.
Therefore if it was similar car to mine doing similar speed, I would choose to hit oncoming car head on that a tree. (just because it's way better to hit a wall than a tree).

But if there was big difference in weight or speed of vehicles (other vehicle much heavier or going much faster) I would probably choose to hit a tree.

F.e. If small car weighting 1 tonne doing 50km/h would hit another car doing the same speed but weigting 2 tonnes, effect would be like heavier car hit a wall at 33.3 km/h while lighter car like it would hit a wall at 66.6 km/h.
And this additionally means that twice the speed of accident, makes accident 4 times worse, as there is 4 times more energy to absorb.

af_thefragile

CiniO wrote: »

If 2 cars each at 50km/h crash head on, assuming they are the same kind of cars (the same crumple zones, the same weight, etc) it will be equal effect as each of them hitting the wall at 50km/h.
Therefore if it was similar car to mine doing similar speed, I would choose to hit oncoming car head on that a tree. (just because it's way better to hit a wall than a tree).

But if there was big difference in weight or speed of vehicles (other vehicle much heavier or going much faster) I would probably choose to hit a tree.

F.e. If small car weighting 1 tonne doing 50km/h would hit another car doing the same speed but weigting 2 tonnes, effect would be like heavier car hit a wall at 33.3 km/h while lighter car like it would hit a wall at 66.6 km/h.
And this additionally means that twice the speed of accident, makes accident 4 times worse, as there is 4 times more energy to absorb.

So moral of the story is to buy a Hummer!!

AugustusMinimus

robbie7730 wrote: »

In terms of reducing impact level, probably. But in reality avoiding hitting another car would be preferable.

If you have morals, you'll go for the tree.

Bruthal

AugustusMinimus wrote: »

If you have morals, you'll go for the tree.

I thought thats what I said more or less:)

Although if it was the other drivers stupidity, maybe it would be better to hit them than watch them see you hit a tree, and get away with it.

thecomedian

Your more than likely dead either way!

unkel

Don't underestimate trees. Hitting even a small one is probably worse than hitting a solid concrete wall

BrianD3

unkel wrote: »

Don't underestimate trees. Hitting even a small one is probably worse than hitting a solid concrete wall

Yes, and trees with relatively small diameter (say 20 cm) but which are strong enough to not break when hit by a car might be the worst ones - due to the impact being concentrated on a small area of the car's structure. A huge tree with a 1 metre diameter trunk might be more forgiving.

Also, as bad as it is to hit a tree head on, hitting one side on is much worse.

Opel Omega vs pole, 98 km/h
http://www.youtube.com/watch?v=8QsKZWYYjfE#t=03m23s

af_thefragile

If only all cars were built like modern WRC cars.

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

Both driver and co-driver escaped with only minor bruises!

TheChizler

CiniO wrote: »

If 2 cars each at 50km/h crash head on, assuming they are the same kind of cars (the same crumple zones, the same weight, etc) it will be equal effect as each of them hitting the wall at 50km/h.
Therefore if it was similar car to mine doing similar speed, I would choose to hit oncoming car head on that a tree. (just because it's way better to hit a wall than a tree).

But if there was big difference in weight or speed of vehicles (other vehicle much heavier or going much faster) I would probably choose to hit a tree.

F.e. If small car weighting 1 tonne doing 50km/h would hit another car doing the same speed but weigting 2 tonnes, effect would be like heavier car hit a wall at 33.3 km/h while lighter car like it would hit a wall at 66.6 km/h.
And this additionally means that twice the speed of accident, makes accident 4 times worse, as there is 4 times more energy to absorb.

There's a bit myth out there, encouraged by the driver theory test, that hitting another car at the same speed will result in a relative speed of twice their individual speed. While this is true for cars passing by each other, it's completely different in a head on collision scenario.

That said when you account for debris there are probably bits and pieces flying through windscreens at a relative speed greater than either individual speed, but hardly anywhere near twice the speed.

Good point about twice the speed meaning four times the energy disappated in a crash. This is also true of stopping distance. This led to an old physics professor of mine's favourite line, speed doesn't kill, speed squared does.

bazz26

What a bizzare thread. This is like asking would you prefer a kick to the head or a kick in the nuts.

Victor

Hitting a wall is generally safer than hitting a tree or pole (unless it is a very small tree/pole). The wider the object you hit, the more the pressure (force divided by contact area) is dissipated.

bazz26 wrote: »

What a bizzare thread. This is like asking would you prefer a kick to the head or a kick in the nuts.

Well, sometimes it isn't a choice that you are going to be hit, but you get to choose where.

Important road safety feature here:



The pole has a crumple zone of it's own - the vehicle starts decelerating before it hits the pole.

Stop the sniggering down the back

BrianD3

bazz26 wrote: »

What a bizzare thread. This is like asking would you prefer a kick to the head or a kick in the nuts.

Several variables involved - but given the choice, most likely nuts.

If people made better decisions in the seconds immediately before an inevitable crash I've no doubt that some lives would be saved.

Motorbikes are often very bad to hit, often travelling at high speed and will cut through a car. HGVs are probably the worst thing to hit, even a stationary HGV is bad but when its coming towards you at 40 or 50 mph there is great potential for death and its preferable to hit almost anything else.

I drive on the below road sometimes and am vary of meeting HGVs on this section because the Armco barrier means my best escape route is cut off
http://maps.google.ie/maps?q=killydoon+cavan&hl=en&ll=53.893516,-7.445812&spn=0.028729,0.181103&safe=off&hnear=Killydoon,+County+Cavan&t=m&z=13&layer=c&cbll=53.893544,-7.445849&panoid=NFs1NWmfy5Bo8pkiEj8fhA&cbp=11,0,,0,0

Imagine if you are driving here and instead of meeting a Punto as in the pic you meet a truck with the driver having a heart attack. Brake hard and hope for the best? Try to drive through the Armco? Try to drive off the other side of the road where there is no barrier?

smemon

Would you prefer to have a tonne of feathers or a tonne of bricks fall on top on you?

mathepac

smemon wrote: »

Would you prefer to have a tonne of feathers or a tonne of bricks fall on top on you?

Like the thread responses so far I have to say that "there are so many variables in your question it's hard to answer definitively". Are the feathers in a solid block in a vacuum-compressed container? Are the bricks loose or are they strapped to a pallet? When you say "fall on top of me" do they just topple over at ground level or are they dropped from a height onto my head? Am I standing on a trampoline, on grass or on concrete? Are the bricks actual house bricks or rubber / soft plastic props used in films, which would make a huge difference if they were dumped loose even from a height?

The simple answer to the OP is that a driver would want to be brain-dead to choose to hit a tree. Trees kill. Trees killed the late great Joey Dunlop and trees break even specially prepared rally cars, as was pointed out above. Even hitting a brick / block / stone wall is preferable to hitting a tree, as there is virtually no such thing as a "solid concrete wall" these days apart from bridge / railway abutments and supports. Walls absorb energy and collapse, trees don't. Concrete block walls are inherently unstable which is why regs require that supporting piers be constructed every 8/9 mtrs to stop the wall collapsing under its own weight. Lamp-posts, sign posts etc. are meant to be energy dissipating and snap off at ground level when struck (not the cast iron Victorian ones in Dublin though!).

As has already been pointed out, contrary to the messed up physics in some official publications, two cars meeting head-on at 100kph do not dissipate the energy of one car hitting a solid surface at 200 kph, they dissipate cloer to the energy of one car at 100 kph.

Also contrary to certain campaign ads, speed does not kill, de-celleration from speed and the resultant energy dissipation does.

BrianD3

mathepac wrote: »

Like the thread responses so far I have to say that "there are so many variables in your question it's hard to answer definitively".

The simple answer to the OP is that a driver would want to be brain-dead to choose to hit a tree. .

I agree with most of your post but these two statements seem to conflict. Compare the Laguna tree crash (55 mph) I posted earlier with this Yaris vs Camry crash (both doing 40 mph) Check out the intrusion into the Yaris and the way it is forced backwards.

https://www.youtube.com/watch?v=vcTf78b8WfY

Would it be braindead to pick the Laguna crash over the Yaris crash in this instance.

Joe 90

af_thefragile wrote: »

So moral of the story is to buy a Hummer!!

In fact, when people say they want a big car because they will feel safer, that is the reason.

Victor

BrianD3 wrote: »

Try to drive through the Armco?

Only one way to do that in a car.

Pottler

Victor wrote: »

Hitting a wall is generally safer than hitting a tree or pole (unless it is a very small tree/pole). The wider the object you hit, the more the pressure (force divided by contact area) is dissipated.

Well, sometimes it isn't a choice that you are going to be hit, but you get to choose where.

Important road safety feature here:



The pole has a crumple zone of it's own - the vehicle starts decelerating before it hits the pole.

Stop the sniggering down the back

I probably try and squeeze through the crack, sorry, gap.

mathepac

BrianD3 wrote: »

...
Would it be braindead to pick the Laguna crash over the Yaris crash in this instance.

I can't see the the last utube thing you posted as my mobile B/B is slow right now but the general rule of thumb is to pick cars that have engines and gearboxes located far away from you to avoid big nasty heavy metal things hitting you and to avoid SUVs as they tend to fall over and reduce survivability, moose tests notwithstanding

Pottler

mathepac wrote: »

I can't see the the last utube thing you posted as my mobile B/B is slow right now but the general rule of thumb is to pick cars that have engines and gearboxes located far away from you to avoid big nasty heavy metal things hitting you and to avoid SUVs as they tend to fall over and reduce survivability, moose tests notwithstanding

Best to go for a Peugeot so, my ones engine and gearbox are currently 15 miles away being fixed - should be dead safe in a collision.

dr.fuzzenstein

Two cars hitting head on at 50 mph is exactly the same as hitting a wall at 50 mph.
This whole "It's as bad as hitting a wall at 100 mph" is an old wife's tale.

http://www.physicsforums.com/showthread.php?t=456239&page=2

The crash is effectively at 50 mph, not 100 mph. Think of it in terms of energy. If you have one car hitting a wall at 50 mph, you have the energy from that one car (let's call it E), and it is dissipated by that one car (the wall is stationary). If you have two cars moving at 50 mph, they both have energy E, but the mass is also doubled, so you are dissipating twice the energy but with twice the mass.

And throw some Mythbusters in there too:

http://mythbustersresults.com/mythssion-control

edit:

This seems at least true for cars of equal mass. If you drive a Punto and a truck hits you, you will still end up a smear on the road.

Bruthal

af_thefragile wrote: »

If only all cars were built like modern WRC cars.

Both driver and co-driver escaped with only minor bruises!

Not too many head on collisions in rallying though

mickdw

I think the whole big car v small car is ignored in modern crash safety testing.

2 identical cars hitting head on at 50 kph each is similar to hitting a concrete wall at 50 kph. In this accident if one car was much heavier/larger, the deceleration forces experienced will be much less in the heavier car and if they hit straight on, the heavy car would push the other backwards from impact point resulting in the more extreme accident for the occupants of the small car.

slimjimmc

It's not just weight, height is a critical factor too when considering car v tree. The main frontal crumple zones are generally at bumper level so even a small difference in bumper height between car could allow the higher car 'ride' over this structure in a car-on-car collision.

mathepac

Pottler wrote: »

I probably try and squeeze through the crack, sorry, gap.

Fair play but how do they know she's a Pole? :rolleyes:

seanmacc

I'd probably go for the car for the one simple reason that if I was to hit the tree I wouldn't have a leg to stand on in claiming off the other cars insurance (assuming it was their fault).
Although that is playing roulette with how safe your car is in a head on crash

Bobo78

uberalles wrote: »

If faced with a car driving towards you is a hitting a tree a better option?

I've heard that a head on crash doubles the speed so is a solid tree a better idea ?

Hopefully I never have to choose but just wondering

If I had to go I d rather go into the tree rather than taking someone else innocent with me.

Dartz

Depends.

Big fat oak versus Tin-box mini.... whoever's in the mini's gonna have a bad time
Light pole versus Audi Q7..... someone's going to lose phone service.

Frankly, I don't think anybody'd have time to do much beyond put the right foot to the middle pedal as hard as possible and wish they'd bought the brown interior before impact...