To brake or not to brake

[gfun]

Sat here on the night shift and my neck is playing up from a whiplash injury back at the end of August which set me thinking on what is best to do in a situation where you are sat unable to move waiting for the car behind to hit.

You cant move out the way you hear the tyres screeching along you can see the car getting bigger and …. Crunch.

What is best to brake or not to brake?

We all understand the concept of 3 collisions - Car hits object passenger hits inside of car organs hit inside of body.

But does anyone know of research on the best way to dissipate the energy in a one car stationary crash?

If you did not brake then certainly the cars would be damaged less but would the passenger would get a bigger load from the faster acceleration.

If you did brake then the energy would be dissipated into the road via the car but would the impact on the passenger be lessened (same energy passing through the car just being dissipated in a different way)

But then we have not considered the car in front?

Why am I interested?

Well it’s the third time it’s happened to me so it’s very likely to happen again and if it has not already happened to you then it probably will soon.

In police driver training what is said on this (that’s the link to this bit)

[outlaw]

well if you brake the body is not relaxed.
and you more likely too be hurt.

best think is to just try to relax not too much you can do.

not easy to do ill grant you.

but thats why drunk drivers offten come off best in a crash.
]
than everyone else

plus set your head rests in the right place as most of the neck damage is done with the backward movement.

[Derek Smith]

Hmn, an interesting question.

I've always reckoned:

Handbrake on so that the impact is absorbed via deformation rather than acceleration of your car so as to lower the risk of whiplash;

Foot off brake peadal as it will not be there once the collision occurs;

Hands in your lap as inuries to hands and thumbs are quite common;

Relax.

I've been a passenger in two accidents where there was some notice of the impact and both times it seemed as if I had all the time in the world to prepare (but not enough time to get out of the car) and I had the impression of thinking very clearly. So, if we can come up with some definitive answers, they should be of use.

According to my driver in one accident I had enough time to swear at him as well.

Derek

[Mrs Fish]

Interesting indeed, James speaking;

I agree with Derek. Handbrake on only will not give as much friction as with all the brakes on so it will increase the time taken to dissipate the energy hence lower forces acting on the body. No handbrake would result in the car being punted into other traffic.

Headrests are very important probebly the most important.

When you do have an unavoidable accident your brain slows everything down. In my only big accident where I was a passenger we were doing about 30-40 and it took ages to have the impact, luckily we were okay. An old numpty granny pulled right accross my mate and we T-boned her, spun her round and put her car on the pavement and we did 80 yards of spinning down the road.

rambling now

[rude girl]

I'd say the handbrake on option is the best, because you have already said you have nowhere to go to get out of the way. If you don't have the brake on, then the rear end collision will cause you to hit whatever's in front (I assume another car) with greater momentum and you get two consecutive loads on your body, in opposite directions, which can't be good.

[trooper1212]

One thing you can do to try and not even get into this situation. When you stop at a queue of traffic, stop a car length behind the car in front.
As you say, you can have a suprising amount of time when you are aware that a big bang is coming, that car length could be all you need to do something about it.

[outlaw]

if ther enoutgh room to do it angel the car abit when stoping.

if you are hit the car will spin causing less that if it hit you dead in the back

[rumpelstiltskin]

In my situation 16 years ago i was sitting at the toll at the Forth Road Bridge in Scotland paying my toll,i was just getting my change back when some dick ploughed into the back of me at speed!Not even time or expecting to think brakes or no brakes and i saw him coming in rear view!, but my hand was out the window,i've suffered from a neck complaint ever since,this dick that ploughed into the back of me was in the RAF!Yes folks,he's piloting planes over your houses,i can still remember the dicks name after 16 years,Wayne Baumber.If anyone knows him give him an f'ing big slap from me,thanks!

>> Edited by rumpelstiltskin on Sunday 12th October 13:51

[gfun]

Thanks for this stuff

Along the lines of my thoughts.

The maths says that the heavier your car the better off you will be – so we should all go out and buy a RR :-)

However if your in your Fiat Panda energy dissipation is a major problem as you weigh almost zilch – the only way to make your car act theoretically heaver is to increase the resistance to the road – brakes on.

That was my theory however there will be a huge shock wave being transmitted through the car – and hopefully around you.

The only formulas I have found only include speed weight and resistance – so you end up with a 3 collision - formula car one (numpty) moving from x-y car two (target) being hit and moving from x-y and then your body x-y then y-x on rebound from belts, bags and dash. This works out in theory as best plan is to brake hard and keep on them.

However then you have to bring in the fact you probably wont be around (conscious) for the end of the accident (I did not even know I had been pushed into the second car till she told me) so I like the hand brake idea even if it likely the rear wheels will lift.

The fact that you will be tense is good to remember to try and relax (yes I was able to turn to my passenger and say this is going to hurt) like the arms folded off steering wheel have seen plenty of bust hands. And now have a fetish about correctly adjusted headrests

But its all a theory and not an accelerometer in a crash test dummies head. Where I suspect that with crumple zones to mitigate the effects of a shock wave well designed seats to lower the sudden acceleration of the body, you may just be better off rebounding away letting the acceleration of the car absorbed the energy rather than the car body (this argument fails when you are parked behind a bus but helps if you consider outlaws suggestion of the angle).

Second time round I was in a fiesta being hit by a 5 Series BMW – (worst case small thing being hit by big thing scenario) braking was done for me by the car in front as I hit it. My seat was torn of its mountings I had friction burns and bruises from the belt and torn muscles in chest and legs where the floor came up.

I’m beginning to feel what you do depends on what car your in, is it modern well designed with a good safety rating and then what is in front of you.

Really need some data on this one.


>> Edited by gfun on Sunday 12th October 17:55

[outlaw]

the fact you turned you head too the passager,may have caused more neck problems.

Than I would have done if it was strait ahead.