Why don't they do crash tests where the target is moving?

[Strk]

I was recently watching Fifth Gear (I think it was the one from two weeks ago) and they crashed a Land Rover Discovery into a Renault Espace (A minivan), both doing 40mph. It really got me thinking, why don't they do crash tests with both vehicles moving? Especially with the target being a larger vehicle. Personally, I'd like to see how well a Honda Fit would hold up against an Explorer.

*edit* Fixed

 

[sniperruff]

im pretty sure they have done similar tests.

that was a renault espace, not honda.

 

[jumpr]

The only thing that changes when the target is moving is the speed of the crash. Crashing into a stopped car head-on at 60 mph is roughly the same as crashing head-on into a car when you're both moving at 30 mph. I don't have a physics background though, so I'm just going by conventional wisdom.

I think frontal-offset crashes are some of the best indicators of how cars perform in real-world situations.

 

[sniperruff]

Originally posted by: jumpr
The only thing that changes when the target is moving is the speed of the crash. Crashing into a stopped car head-on at 60 mph is roughly the same as crashing head-on into a car when you're both moving at 30 mph. I don't have a physics background though, so I'm just going by conventional wisdom.

I think frontal-offset crashes are some of the best indicators of how cars perform in real-world situations.

it's not the same when the 2 objects have different mass, ie) an explorer and a fit

 

[Strk]

Originally posted by: jumpr
The only thing that changes when the target is moving is the speed of the crash. Crashing into a stopped car head-on at 60 mph is roughly the same as crashing head-on into a car when you're both moving at 30 mph. I don't have a physics background though, so I'm just going by conventional wisdom.

I think frontal-offset crashes are some of the best indicators of how cars perform in real-world situations.

Yeah, that's another thing they did on Fifth Gear though. It was an offset crash, but even then, they were both big vehicles. I'd just like to see what a 2500lbs car does when it gets hit by a 6000lbs SUV. There are so many safety features out there, I want to see them in action.

 

[0roo0roo]

meh, last weeks fifthgear test was a bit lousy. its like they set it up to make the mini van look good. of course the van bashed the hell out of that old suv, vans are freakin heavy and well designed for such impacts. to be fair they should have tested it with a new suv. then perhaps toss in one of those small euro cars in for a bash.

 

[MmmSkyscraper]

I thought you were talking about pedestrians

 

[Ornery]

Originally posted by: sniperruff

it's not the same when the 2 objects have different mass, ie) an explorer and a fit

It's called crash incompatibility, and it's downplayed because it doesn't fit the greenie's econobox utopia.

Originally posted by: jumpr

...Crashing into a stopped car head-on at 60 mph is roughly the same as crashing head-on into a car when you're both moving at 30 mph...

Two cars (of the same weight) crashing into each other head on at 30MPH each, is the same as hitting a fixed barrier at 30MPH. A stopped car is not the same as a fixxed barrier, because it will "give".

 

[Squisher]

Originally posted by: sniperruff

Originally posted by: jumpr
The only thing that changes when the target is moving is the speed of the crash. Crashing into a stopped car head-on at 60 mph is roughly the same as crashing head-on into a car when you're both moving at 30 mph. I don't have a physics background though, so I'm just going by conventional wisdom.

I think frontal-offset crashes are some of the best indicators of how cars perform in real-world situations.

it's not the same when the 2 objects have different mass, ie) an explorer and a fit

This all can be done through calculation and applied to car hitting a stationary target.

 

[Strk]

Originally posted by: Squisher

Originally posted by: sniperruff

Originally posted by: jumpr
The only thing that changes when the target is moving is the speed of the crash. Crashing into a stopped car head-on at 60 mph is roughly the same as crashing head-on into a car when you're both moving at 30 mph. I don't have a physics background though, so I'm just going by conventional wisdom.

I think frontal-offset crashes are some of the best indicators of how cars perform in real-world situations.

it's not the same when the 2 objects have different mass, ie) an explorer and a fit

This all can be done through calculation and applied to car hitting a stationary target.

Really? I've never been big with physics, so any help would, well, help

 

[Born2bwire]

Originally posted by: Strk

Originally posted by: Squisher

Originally posted by: sniperruff

Originally posted by: jumpr
The only thing that changes when the target is moving is the speed of the crash. Crashing into a stopped car head-on at 60 mph is roughly the same as crashing head-on into a car when you're both moving at 30 mph. I don't have a physics background though, so I'm just going by conventional wisdom.

I think frontal-offset crashes are some of the best indicators of how cars perform in real-world situations.

it's not the same when the 2 objects have different mass, ie) an explorer and a fit

This all can be done through calculation and applied to car hitting a stationary target.

Really? I've never been big with physics, so any help would, well, help

You would do so through the use of momentum, which is what one would use when calculating the effects of collisions. Just using Galilean transformations and momentum probably is enough to simulate the motion of a given second vehicle. One point to note though is that you would need to preserve the orientation of the cars with respect to how they would be traveling. This could be done by rotating the stationary car. I'm sure the whole process would be slightly more involved than this but for a general case this how I would do it.

 

[Strk]

That's interesting, although it still leaves the issue of the impact of a much larger vehicle, doesn't it?

 

[sniperruff]

Originally posted by: Ornery

Originally posted by: sniperruff

it's not the same when the 2 objects have different mass, ie) an explorer and a fit

It's called crash incompatibility, and it's downplayed because it doesn't fit the greenie's econobox utopia.

Originally posted by: jumpr

...Crashing into a stopped car head-on at 60 mph is roughly the same as crashing head-on into a car when you're both moving at 30 mph...

Two cars (of the same weight) crashing into each other head on at 30MPH each, is the same as hitting a fixed barrier at 30MPH. A stopped car is not the same as a fixxed barrier, because it will "give".

they crashed a smart with a mercedes S-class last year... the S-class was totalled and the smart remains intact.

but i think these tests are impossible... how many cars are out there if they want to crash each one head on?

 

[Ornery]

In Europe's five-star crash rating system, the smarts get three stars.

• "On the other hand," he says, "they are small and lightweight and cannot protect you" as well as a larger car. "Fatalities are much higher with small, lightweight vehicles."

The Mercedes grill costs more than an entire "Smart", so it's not hard to believe it would be considered totaled. It's also made to crumple, which is not the case with America's best selling vehicles.

 

[Born2bwire]

Originally posted by: Strk
That's interesting, although it still leaves the issue of the impact of a much larger vehicle, doesn't it?

No it doesn't. Momentum takes into account the mass and velocity of the objects and any collision still follows the conservation of momentum.

 

[0roo0roo]

Originally posted by: sniperruff

Originally posted by: Ornery

Originally posted by: sniperruff

it's not the same when the 2 objects have different mass, ie) an explorer and a fit

It's called crash incompatibility, and it's downplayed because it doesn't fit the greenie's econobox utopia.

Originally posted by: jumpr

...Crashing into a stopped car head-on at 60 mph is roughly the same as crashing head-on into a car when you're both moving at 30 mph...

Two cars (of the same weight) crashing into each other head on at 30MPH each, is the same as hitting a fixed barrier at 30MPH. A stopped car is not the same as a fixxed barrier, because it will "give".

they crashed a smart with a mercedes S-class last year... the S-class was totalled and the smart remains intact.

but i think these tests are impossible... how many cars are out there if they want to crash each one head on?

did they smack them together with both moving? or did they push the smart into the merc. decel forces should be much higher with the lighter car.

 

[zugzoog]

Originally posted by: Strk
I was recently watching Fifth Gear (I think it was the one from two weeks ago) and they crashed a Land Rover Discovery into a Renault Espace (A minivan), both doing 40mph. It really got me thinking, why don't they do crash tests with both vehicles moving? Especially with the target being a larger vehicle. Personally, I'd like to see how well a Honda Fit would hold up against an Explorer.

*edit* Fixed

I suspect that when you have a stuff load of very expensive and immobile detection equipment (ie. high speed cameras) and the fact that you only get one shot at the collision, it is a good idea to know exactly where the collision is taking place. Not too mention that the moving vehicle is usually running on a track so that the precise target speed is achieved and can be measured accurately. You also have a stuff load of sensors on each car, sending a lot of information so this means you need cables (you might be able to move to wireless, but as you only get one shot, it needs to be ultra reliable).

The different masses and how they behave is relatively easy to calculate (ie. calculate the movement of the centre of mass position for the two cars as a whole and plot how each of the cars deviates from this.).

 

[Strk]

Originally posted by: 0roo0roo

Originally posted by: sniperruff

Originally posted by: Ornery

Originally posted by: sniperruff

it's not the same when the 2 objects have different mass, ie) an explorer and a fit

It's called crash incompatibility, and it's downplayed because it doesn't fit the greenie's econobox utopia.

Originally posted by: jumpr

...Crashing into a stopped car head-on at 60 mph is roughly the same as crashing head-on into a car when you're both moving at 30 mph...

Two cars (of the same weight) crashing into each other head on at 30MPH each, is the same as hitting a fixed barrier at 30MPH. A stopped car is not the same as a fixxed barrier, because it will "give".

they crashed a smart with a mercedes S-class last year... the S-class was totalled and the smart remains intact.

but i think these tests are impossible... how many cars are out there if they want to crash each one head on?

did they smack them together with both moving? or did they push the smart into the merc. decel forces should be much higher with the lighter car.

They were both doing 30mph and they did it as an offset crash. The Smart Car was tossed on to its side, but they were ultimately showing that its cage would hold its shape, which it did. Fifth Gear did the same thing with a Smart Car and slammed it into a 20 ton barrier doing 70mph. Again, it held its shape, but Fifth Gear pointed out that, even though the car was relatively secure, your organs would have been in trouble because of the decelleration.

 

[Ornery]

Originally posted by: 0roo0roo

did they smack them together with both moving? or did they push the smart into the merc. decel forces should be much higher with the lighter car.

Sheesh, I put a link to the whole damn video (Why I ever bother, I'll never know):

1. In Europe's five-star crash rating system, the smarts get three stars.