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

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    #32
    TheChizler
    Registered Users Posts: 9,420 ✭✭✭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.


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    #33
    bazz26
    Registered Users Posts: 51,141 ✭✭✭✭bazz26


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


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    #34
    Victor
    Registered Users Posts: 78,273 ✭✭✭✭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. :confused:
    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:

    224305.jpg

    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


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    #35
    BrianD3
    Registered Users Posts: 8,289 ✭✭✭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. :confused:
    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?


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    #36
    smemon
    Registered Users Posts: 3,467 ✭✭✭smemon


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


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    #37
    mathepac
    Banned (with Prison Access) Posts: 4,991 ✭✭✭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.


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    #38
    BrianD3
    Registered Users Posts: 8,289 ✭✭✭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.


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    #39
    Joe 90
    Registered Users Posts: 890 ✭✭✭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.


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    #40
    Victor
    Registered Users Posts: 78,273 ✭✭✭✭Victor


    BrianD3 wrote: »
    Try to drive through the Armco?

    Only one way to do that in a car.

    iHrp2.gif


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    #41
    Pottler
    Closed Accounts Posts: 5,073 ✭✭✭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:

    224305.jpg

    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.


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    #42
    mathepac
    Banned (with Prison Access) Posts: 4,991 ✭✭✭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 :D


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    #43
    Pottler
    Closed Accounts Posts: 5,073 ✭✭✭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 :D
    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.


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    #44
    dr.fuzzenstein
    Banned (with Prison Access) Posts: 16,635 ✭✭✭✭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.


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    #45
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭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


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    #46
    mickdw
    Registered Users Posts: 23,270 ✭✭✭✭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.


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    #47
    slimjimmc
    Registered Users Posts: 7,787 ✭✭✭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.


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    #48
    mathepac
    Banned (with Prison Access) Posts: 4,991 ✭✭✭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:


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    #49
    seanmacc
    Closed Accounts Posts: 771 ✭✭✭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


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    #50
    Bobo78
    Closed Accounts Posts: 556 ✭✭✭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.


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    #51
    Dartz
    Registered Users Posts: 4,368 ✭✭✭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...


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    #52
    peasant
    Registered Users Posts: 17,819 ✭✭✭✭peasant


    Dartz wrote: »
    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...

    Actually, that's not quite correct.

    You know how people say that in times of extreme danger time passes like in slow motion ...it's true. Under extreme stress your body releases all sorts of substances (adrenalin among them) that temporarily give you "super powers". Not just extra physical strength, but also a few extra GB of brain power. Time seems to slow down because your brain suddenly (and temporarily) goes into overdrive and processes information at several times the normal speed.

    Use that time, don't freeze.
    Don't focus on the tree/car thinking "please don't let me hit that car / **** I'm gonna hit that tree".
    Focus on the gap / the least painful option instead and chances are you might just be able to make that last correcting maneuvre and survive that acident.


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    #53
    Matt Simis
    Registered Users Posts: 8,718 ✭✭✭Matt Simis


    peasant wrote: »
    Focus on the gap / the least painful option instead and chances are you might just be able to make that last correcting maneuvre and survive that acident.
    Agreed.
    I think glancing the tree then hitting the car might be best for me. But generally as pointed out, trees are lethal.


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    #54
    soups05
    Registered Users Posts: 1,086 ✭✭✭soups05


    for me i would hit the other car everytime.if i'm in the wrong (and i'm a man so never wrong :D) then they can claim from me. if i'm in the right then i claim from them. the tree won't have insurance cover (they never do).

    some posters raised a good point about killing innocent passengers or drivers.

    consider this

    http://www.feeleminds.com/forum/a-moral-dilemma-t9213.html


    short version is they should'nt be on my side of the road so sod em :D


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    #55
    BrianD3
    Registered Users Posts: 8,289 ✭✭✭BrianD3


    mickdw wrote: »
    I think the whole big car v small car is ignored in modern crash safety testing.
    Recently the ADAC and NHTSA have done some frontal tests with moving sled barriers instead of "immovable" ones. This might be a step in addressing the issue of big car and small cars getting the same rating but the big car probably being safer.

    In the NHTSA test the sled is moving but the car is stationary. Dodge Ram and Chevy Cruze videos below. I think the Ram's far greater weight should give it an advantage here but according to the text the Ram driver seems to experience similar forces to the Cruze driver. Obviously if the Ram and Cruze were moving as well as the sled then that would be a different scenario again.

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


    https://www.youtube.com/watch?v=g2thztKHNFU


    The ADAC has tested 4 small cars against a sled, both the sled and the cars were moving.

    https://www.youtube.com/watch?v=KlGYwCQ_Ge4


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    #56
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    mathepac wrote: »

    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.

    Two similar cars direct head on at 100kph will probably dissipate double the energy of a single 100kph crash direct into a solid immovable surface.


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    #57
    Pottler
    Closed Accounts Posts: 5,073 ✭✭✭Pottler


    mathepac wrote: »
    Fair play but how do they know she's a Pole? :rolleyes:
    Insert reference to the pole she'd give any red-blooded male.
    On a more serious note, I've hit a steel pole at 60kph, driving an older model Nissan primera which I pointed into the verge while avoiding a nut in a Celica that just kept coming as he messed up an overtaking manouever-head on on my side of the road, - apart from breaking a finger on the steering wheel, myself and my 4 passengers were aok, if somwhat emotional and ill disposed towards the Celica driver. If I had taken option 2, which was keep driving straight and hit the celica head on, I doubt the outcome would have been so rosy. And yes, I had time to make a choice. And no, I did not expect a skinny looking steel signpost to exert quite such a force on the car - it ripped off the passenger side front wheel and wrote the car off. I was fond of that car....grr


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    #58
    SouperComputer
    Registered Users Posts: 6,949 ✭✭✭SouperComputer


    Its a tough question to answer, but unless the tree was really feckin wide I'd be making sure I hit the other car as close to dead square on as I could, unless I dont have a passenger, in which case I'd go with the passenger side.


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