Black box' in car crash court case

[Full Noise]

Originally Posted by ray38l

Its worrying if they bring in tracking systems like some private companies have.
A big security company i worked for last year had a system that would tell them everything. They could tell when we were sitting in the drivers seat, how fast we were going, how fast we were accelerating, how hard we were braking, if we had seatbelts on, if we had passengers in the car and how many and all this in real time. Its just worrying how much information governments or company's can know about what people do.

*yawn*
They’ve had this type of information “and more” in some trucks for over twenty years now.

[jpd80]

Police can usually work out impact speeds from the amount of damage done to vehicles,
I see no reason for changing from this method of deduction and I d rather see authorities
dealing with analysing crash data then trusting a bit of onboard wizzardry.

[Bucknaked]

knight rider

[sudszy]

Originally Posted by ryanstev

He was the significantly faster car, at the collision he slowed from the impact, the other driver was instantly shunted backwards.

All other things being equal its only the relative speed and mass of the two vehicles that is relevant to a collision. its the vehicle with more mass that will have the greater survivability, the mass of the car is the major factor that dictates the change in velocity of the occupants before and after the collision.

So whether we have
A: the two cars colliding at 50km/h headon

or B:
one car doing 100km/h hitting a stationary car

the collision is the same, the forces on the occupants are the same.

(Possibly one thing Im not sure on, would the air bag go off in a new vehicle in the stationary car in case B? if not, collision worse for occupants of stationary car)

However, in this case all things were not equal, a 73 mercedes, Im assuming without airbags is most likely not as surviveable as newer offerings.

Was originally going to comment on the black box aspect, but will be back later for that.

[GS608]

Originally Posted by sudszy

All other things being equal its only the relative speed and mass of the two vehicles that is relevant to a collision. its the vehicle with more mass that will have the greater survivability, the mass of the car is the major factor that dictates the change in velocity of the occupants before and after the collision.

So whether we have
A: the two cars colliding at 50km/h headon

or B:
one car doing 100km/h hitting a stationary car

the collision is the same, the forces on the occupants are the same.

(Possibly one thing Im not sure on, would the air bag go off in a new vehicle in the stationary car in case B? if not, collision worse for occupants of stationary car)

However, in this case all things were not equal, a 73 mercedes, Im assuming without airbags is most likely not as surviveable as newer offerings.

Was originally going to comment on the black box aspect, but will be back later for that.

Wrong..two cars colliding at 50kph head on does not equal a single car hitting a stationary object at 100kph.

[DJR-351]

Originally Posted by 5.0

Wrong..two cars colliding at 50kph head on does not equal a single car hitting a stationary object at 100kph.

Consider two scenarios:

Two identical vehicles (same size and mass) travel at the same speed, let's say 50 km/h, in opposite directions, and they collide with each other head-on.
One of those vehicles hits a rock wall (which doesn't break nor budge in any significant way) head-on at 50 km/h.
From the point of view of one of the vehicles, which collision is more severe?

Most people would instantly answer that the first collision is more severe because the effective collision speed is 100 km/h, and thus the collision has twice as much force than the second collision, which happens only at 50 km/h.

This answer is wrong, wrong, and utterly wrong. Many people just don't get this one, not even people who should know better. I can't even count how many times I have heard people getting this one wrong.

The most prominent and severe case which I have seen was Jamie Hyneman from the show MythBusters getting this exact problem wrong in their "demolition derby special" episode, where he stated that two trucks travelling at 50 mph each and colliding head-on were subject to a collision force equivalent to hitting a rock wall at 100 mph. Maybe he is not a phycisist, but nevertheless he of all people should know this.

The correct answer is: The two collisions are completely equivalent. From the point of view of one of the vehicles it makes absolutely no difference whether it hits a rock wall at 50 km/h or another identical vehicle which was traveling at the same speed in the opposite direction. The amount of force applied to the vehicle is the same in both situations.

(Ok, in reality there will be some differences because the consistency of a rock wall is very different from a consistency of a vehicle, but this only means that hitting the rock wall will be more severe than hitting the other car, although probably not by a lot.)

I know that no matter how much this is explained, some people just don't get it. They just can't get rid the misconception that the two-vehicle collision must have double the force. There are a few things which might make it easier to accept:

When the vehicle hits the rock wall at 50 km/h, the rock wall causes a force large enough to stop the vehicle right there. In other words, the vehicle hits the rock wall with a momentum equivalent to its speed times its mass. Conversely, by Newton's law, at the moment of the collision the rock wall causes an equal force to the vehicle in the opposite direction, causing it to stop. That is, the rock wall causes a force equivalent to the 50 km/h times the mass of the vehicle.

The misconception in the two-vehicle scenario is basically that this applied force is double that, ie. the equivalent to 100 km/h times the mass of the vehicle.

However, think about where this force is coming from in the two-vehicle scenario: It's coming from the second vehicle. But the second vehicle is also traveling at 50 km/h and has the same mass.

So we have two forces: Vehicle 1 applies the equivalent of 50 km/h times its mass to vehicle 2, and vehicle 2 applies an equal force to vehicle 1. This causes both vehicles to stop right there.

Where would the additional 50 km/h times the mass of the vehicle come from? Vehicle 1 cannot apply that force to itself. It's applying it to vehicle 2. So where is it coming from?

The answer is that it's not coming from anywhere because the force applied to vehicle 1 is not 100 km/h times the mass, but only 50 km/h times the mass. The same as with the rock wall.

Think also about this: If you applied a force equivalent to 100 km/h times the mass in the opposite direction of vehicle 1, that would actually make vehicle 1 change direction and go backwards at 50 km/h after the collision. Conversely it would also make vehicle 2 do the same. That doesn't happen.

Think about it like this: If vehicle 1 couldn't "see" what it hits, how can it tell if it hit a rock wall or vehicle 2? The "point of impact" remains stationary in the two-vehicle case, in the exact same way as in the one-vehicle-and-rock-wall case. From the point of view of vehicle 1, there's no difference.

Now, if vehicle 2 was stationary and vehicle 1 hit it at 50 km/h, that would make a big difference compared to the rock wall. That's because now vehicle 2, having the same mass as vehicle 1 (rather than "infinite" mass, as the rock wall), is applying much less force to vehicle 1.

.....

[MAGPIE]

Originally Posted by sudszy

All other things being equal its only the relative speed and mass of the two vehicles that is relevant to a collision. its the vehicle with more mass that will have the greater survivability, the mass of the car is the major factor that dictates the change in velocity of the occupants before and after the collision.

'All other things' are not normally equal in the real world.

As for the vehicle with the greater mass having the greater survivability I have personally seen that disproven on numerous occassions.

[GasoLane]

Originally Posted by Full Noise

*yawn*
They’ve had this type of information “and more” in some trucks for over twenty years now.

Aw Geez dont tell them that. They all think that the Gov is using the very latest in cutting edge technology.

Not something that Trucks have been field testing for them for years.

[MO]

Originally Posted by GasOLane

Aw Geez dont tell them that. They all think that the Gov is using the very latest in cutting edge technology.

Not something that Trucks have been field testing for them for years.

What, its not the latest tech there is.

[billy302]

There would have been other things like skid marks and accident damage to give police information and the conclusions from they reached from this information lead to the warrant for the removal of the black box.
If the black box information supports the accident data then this is conclusive evidence. There is not 1 thing buy itself that convicts, but the inevitable conclusion that the truth is not being told, and the black box data lends credibility to their argument.

[sudszy]

Originally Posted by 5.0

Wrong..two cars colliding at 50kph head on does not equal a single car hitting a stationary object at 100kph.

Well no, if the stationary object is the same car that would be involved in the 50kph head on then Im correct, and that's what I said:

Originally Posted by sudszy

All other things being equal its only the relative speed and mass of the two vehicles that is relevant to a collision. its the vehicle with more mass that will have the greater survivability, the mass of the car is the major factor that dictates the change in velocity of the occupants before and after the collision.

So whether we have
A: the two cars colliding at 50km/h headon

or B:
one car doing 100km/h hitting a stationary CARthe collision is the same, the forces on the occupants are the same.

(Possibly one thing Im not sure on, would the air bag go off in a new vehicle in the stationary car in case B? if not, collision worse for occupants of stationary car)

However, in this case all things were not equal, a 73 mercedes, Im assuming without airbags is most likely not as surviveable as newer offerings.
.

Have a little think about it, do you think colliding with just any stationary object at 100km/h would write off you car? like say colliding with a tissue box?

You are confusing the case for where a the car collides with an immovable object such as a concrete wall.

[sudszy]

Originally Posted by MAGPIE

'All other things' are not normally equal in the real world.

.

Well no there not, that's why the mercedes driver has come off second best here even though the masses of the vehicles were probably similar, not having an airbag in the mercedes would possibly be the biggest discriminator.

[sudszy]

Originally Posted by dom_105

It's a slippery slope alright. It's like the frog in the boiling water. Sooner or later, our freedoms are going to be taken/restricted by increments, one by one.

For those and others that harp on about their freedoms and privacy.......buy your own roads and you can do what you like!

Public roads, what you do on them should be available to authorities, what you do with your partner behind closed doors, your business.

I've got no idea how reliable car black box stuff is for this sort of thing, but if it is proven to be reliable and accurate enough, I have no problems in it being used to prove/disprove ANY driving event/incident.

I can see insurance companies may have a big interest in it, if they can refuse a payout on someone who totals an exotic car or expensive australian 'hoon car" based on how fast the wheels were spinning around the time of the event, then motoring should get cheaper for all of us.

[billy302]

Even on an old EF falcon data can be downloaded from the computer regarding engine revs and gear selection and I believe the G force in a collision, what triggered the airbag.
It is a known fact that hitting another car head on does not multiply the energy of the accident. The energy of that particular vehicle is absorbed by itself and nothing more.
Whether the Mercedes involved had airbags or not is not known, but I would suggest that it would have to be pretty old not to have them since Mercedes have been fitting them to all their cars since the late 70's.
The bottom line in this is the fact that the police don't believe his bulldust about how fast he was going

[maty]

Originally Posted by Full Noise

This is already happening with heavy vehicles. The task force regularly stop trucks and “plug into them” to make sure that limiters aren’t tampered with.

What has our country come to?

The Kenworth I drive is GPS tracked, and that means everything, braking applications, braking distance, deceleration, G forces in corners, the lot.
But, if I were to have some major accident, the police would be kicking the front door of my employer in demanding the data from the vehicle under the “chain of responsibility” laws.

Whether they get this information or not, I’m not sure but they would give it a bloody good try.

They have no right to this from anyone. If they want to convict someone, they can damn well do the investigation themselves, not rely on outside data that in many cases, they have to legal right to.

In my opinion, we are becoming a police state.

We have this at work as well, we have a pendent we have to swipe when we start the truck n they get a reading of who is driving the vehicle.

[sudszy]

Originally Posted by billy302

Whether the Mercedes involved had airbags or not is not known, but I would suggest that it would have to be pretty old not to have them since Mercedes have been fitting them to all their cars since the late 70's.

It was revealed in one of the links.
http://www.stuff.co.nz/national/crim...onvicts-driver

Mercedes have been only been fitting them as standard equipment for ~20 years.
http://www.emercedesbenz.com/autos/m...traint-system/

about 20 years after the car involved was manufactured.

The data released also sites a speed change of 52km/h in 2secs, this is a deacceleration of ~0.74g, entirely consistent with the braking performance of a modern road car at higher speeds.

[2011G6E]

From a post I just made elsewhere here tonight...kind of relevant...

I was chatting to a supervisor tonight, and he had a map up on his computer screen, with several boxes on it with car regos I recognised. They were our work vehicles. I knew of course, as does everyone here, that our cars all have GPS trackers in them, but I didn't know the level of detail they go to.

The list of things they tracked was, of course, location, speed, average speed, "excessive acceleration" (of a kph/second figure), excessive braking (more than 21kph/second...one guy had 34kph/second...obviously a roo jumped out), "violent cornering" (measured as a change of direction of 70 degrees from original course at 50kph or greater), and (amazingly) whether you had not put the handbrake on when parking it..."not securing vehicle correctly", that one was marked as...odd seeing as how they are all automatics...

They keep a full...and I mean full...log of everyones car driving, as we have to fill out log books when we take a car anywhere, so they know who was in the drivers seat.

Most of all, I wonder how long before this sort of GPS tracking is seen as "a good thing" by safetycrats in Canberra...it's getting cheaper and cheaper...

[Jim Goose]

Originally Posted by 2011G6E

From a post I just made elsewhere here tonight...kind of relevant...

I can see why some companies would have GPS trackers in their vehicles.
Unfortunately how many people out there drive their company vehicle in a normal manner? or just thrash the crap out of it? speed, go through red lights, tailgate... etc...

Worse when you have your compnay logo on it and some dill drives like a maniac, hardly good for the companies image

[GS608]

Originally Posted by sudszy

Well no, if the stationary object is the same car that would be involved in the 50kph head on then Im correct, and that's what I said:


Have a little think about it, do you think colliding with just any stationary object at 100km/h would write off you car? like say colliding with a tissue box?

You are confusing the case for where a the car collides with an immovable object such as a concrete wall.

So you're saying that the forces are the same? So in a head on with both cars travelling at 50kph where does the extra 50 kph come from? Your body won't go from 100-0 like they would by hitting a stationary object (movable or immovable) while traveling 100kph.

[vztrt]

Originally Posted by Jim Goose

I can see why some companies would have GPS trackers in their vehicles.
Unfortunately how many people out there drive their company vehicle in a normal manner? or just thrash the crap out of it? speed, go through red lights, tailgate... etc...

Worse when you have your compnay logo on it and some dill drives like a maniac, hardly good for the companies image

I drive my workplace ute quite sensibly as I don't need the BS associated with a fine. Treating like crap wouldn't matter seeing before I started working there this thing wasn't even looked after for basic servicing (was 7000k's over when I got it serviced).

[sudszy]

Originally Posted by 5.0

So you're saying that the forces are the same? So in a head on with both cars travelling at 50kph where does the extra 50 kph come from? Your body won't go from 100-0 like they would by hitting a stationary object (movable or immovable) while traveling 100kph.

where does the extra 50kph come from? Im not sure what you mean, in the 50kph head on, both vehicles and occupants suffer a 50kph change in speed, not a 100kph change in speed.

Originally Posted by 5.0

Your body won't go from 100-0 like they would by hitting a stationary object (movable or immovable) while traveling 100kph.

The only way you get a 100km/h speed change is if you hit something that wont move. If you hit a tissue box you wont slow down at all.
A car doing 100km/h that collides with an identical stationary car will go from 100km/h to 50km/h, the stationary car will go from 0 to 50km/h in the same direction, momentum has to be conserved. Both have suffered a 50km/h speed change, just the same as if they collided head on both doing 50km/h, its the same collision

Perhaps think about the collision taking place in outer space where there is no ground frame of reference.

One vehicle may well consider themselves stationary, and see the other vehicle approaching them at 100km/h, whereas the other looking back at earth considers themselves to be moving at 50km/h and the other vehicle approaching it at 50km/h, the relative velocities are the same......and hopefully you can see that whatever speed each vehicle thinks they are going at will have no effect on the collision