Topic: IIHS Trucks test

[Fobroader]

Mass winning in a collision is a fact.

I'd almost agree, except in a collision with an infinite-mass object, the energy that will be (hopefully) dissipated in the front end, is m*v^2.  The higher m is, the more energy you have to dissipate.  So you really want to be in the JCW in that collision.

As for the previous comment about IIHS not testing for collision avoidance: a) clearly you haven't looked at their website in the past two years or so, because they talk a lot about automation systems to avoid accidents, and b) it goes into their ratings.  Even if it were not a factor, it is definitely a consideration to a rational person.

Pretty sure I am not the only engineer who will tell you folks that the best outcome is a totally-avoided collision.  :-)  Also, I'm not sure why so many people ride around in empty pickup trucks that can't steer and have ox-and-cart suspensions, while consuming huge amounts of fuel.  It seems to me, to be a terrible waste of transportation resources.

Yeah well, so is the pensioner going 20 under the limit in the passing lane with their Corvette......

[Cord]

Mass winning in a collision is a fact.

I'd almost agree, except in a collision with an infinite-mass object, the energy that will be (hopefully) dissipated in the front end, is m*v^2.  The higher m is, the more energy you have to dissipate.  So you really want to be in the JCW in that collision.

As for the previous comment about IIHS not testing for collision avoidance: a) clearly you haven't looked at their website in the past two years or so, because they talk a lot about automation systems to avoid accidents, and b) it goes into their ratings.  Even if it were not a factor, it is definitely a consideration to a rational person.

Pretty sure I am not the only engineer who will tell you folks that the best outcome is a totally-avoided collision.  :-)  Also, I'm not sure why so many people ride around in empty pickup trucks that can't steer and have ox-and-cart suspensions, while consuming huge amounts of fuel.  It seems to me, to be a terrible waste of transportation resources.

What is a real-life example of an infinite-mass object?

[rrocket]

Mass winning in a collision is a fact.

I'd almost agree, except in a collision with an infinite-mass object, the energy that will be (hopefully) dissipated in the front end, is m*v^2.  The higher m is, the more energy you have to dissipate.  So you really want to be in the JCW in that collision.

As for the previous comment about IIHS not testing for collision avoidance: a) clearly you haven't looked at their website in the past two years or so, because they talk a lot about automation systems to avoid accidents, and b) it goes into their ratings.  Even if it were not a factor, it is definitely a consideration to a rational person.

Pretty sure I am not the only engineer who will tell you folks that the best outcome is a totally-avoided collision.  :-)  Also, I'm not sure why so many people ride around in empty pickup trucks that can't steer and have ox-and-cart suspensions, while consuming huge amounts of fuel.  It seems to me, to be a terrible waste of transportation resources.

No.  You want to be in the larger, heavier car.

http://www.iihs.org/iihs/news/desktopnews/new-crash-tests-demonstrate-the-influence-of-vehicle-size-and-weight-on-safety-in-crashes-results-are-relevant-to-fuel-economy-policies

From an FAQ at the IIHS:  Are people less likely to be killed or injured in a bigger, heavier vehicle?

Yes. Driver death rates calculated by IIHS illustrate the real-world advantages of bigger, heavier vehicles. For example, as a group, in 2014 very large cars 1-3 years old had 19 deaths per million registered vehicles, while minicars had 55. Of the 19 vehicles with the lowest driver death rates from the 2008-11 model years during 2009-12, all were midsize or larger. Two-thirds of those with the highest rates were small vehicles or minicars. 2

Improvements in crash protection have made vehicles of all sizes safer, but, as illustrated in the figure below, an advantage persists for bigger vehicles, as measured by shadow, or length times width. Size and weight are highly correlated, so the figure would look similar if weight were used instead.

[ElectricMayhem]

What is a real-life example of an infinite-mass object?

A bridge abutment can be considered infinite-mass in this context.

[Cord]

What is a real-life example of an infinite-mass object?

A bridge abutment can be considered infinite-mass in this context.

Gotcha, thanks. I'm no engineer but find the topic interesting nevertheless.

I suspect it is not as simple as saying that a Mini will be safer than an full-size truck in a collision with a bridge abutment. I would think that differences in width, height, length, materials, etc, etc. may have more effect on outcomes than mass in isolation.

Would it be more accurate to say that, in theory, 3000 lb Mini would be safer than a 6000 lb Mini in a collision with a bridge abutment?

[ElectricMayhem]

No. 

Sadly, you are not picking up what I am laying down here, because what you posted does not address the point I was making.  It is much more complicated than broad statements like "mass is good."  Mass is almost never good.  Every car manufacturer wants to add lightness.

I wonder how the people who buy F-150s for the male enhancement, feel when they kill the woman in the Golf unnecessarily.  I guess they feel nothing at all, because they lack insight.

The best thing is to strike a balance between mass and maneuverability, enrol in car control school every few years, and pay attention to what the instructor is saying.  Buy a good set of winter tires, studded if allowed where you are. And don't buy heavy vehicles with high CofG, that have long stopping distances, and poor emergency steering response.  That will give you the best chance at avoiding an accident in the first place.

[rrocket]

No. 

Sadly, you are not picking up what I am laying down here, because what you posted does not address the point I was making.  It is much more complicated than broad statements like "mass is good."  Mass is almost never good.  Every car manufacturer wants to add lightness.

I wonder how the people who buy F-150s for the male enhancement, feel when they kill the woman in the Golf unnecessarily.  I guess they feel nothing at all, because they lack insight.

The best thing is to strike a balance between mass and maneuverability, enrol in car control school every few years, and pay attention to what the instructor is saying.  Buy a good set of winter tires, studded if allowed where you are. And don't buy heavy vehicles with high CofG, that have long stopping distances, and poor emergency steering response.  That will give you the best chance at avoiding an accident in the first place.

As stated earlier, we were talking car vs car collision....which is generally the scope of the tests IIHS does.  Do people hit bridges or trees?  Sure.  But you're more likely to be involved in another crash with another vehicle.  Which is why they started the off-set crash in the first place as it mimics (to a degree) a head-on crash with another vehicle.  So in this case, mass almost always wins (except technology...and older 50-60s car weighing the same as a new car will come out worse.)

And you argument about those driving a heavy vehicle (an F-150 in your argument) is a bit nonsensical.  What if the person in the Golf was responsible for the crash?  Crossing the center line, drunk, not paying attention, etc.?  On a very basic level (because I'm human) I'd feel somewhat bad.  But I'd feel worse if my wife didn't come home at night and the reason she was saved was that she was driving my large, heavier, luxury car.  This has nothing to do with lack of insight.

And sure, saying "avoiding" the crash is easy.  But it rarely works out that way

And no, car companies didn't go to lighter vehicle for safety.  The biggest motivator behind this was meeting CAFE and MPG targets. 

[johngenx]

Most people in Alberta ride around in full size trucks that don't carry anything heavier or more substantial than the family pack of toilet paper from Costco.  Massive waste of manufacturing resources and fossil fuels.  I wonder of $2.00/L gas would have an impact?

[EV-Light]

I rarely agrees with rrocket but passengers in the bigger heavier vehicle have a higher chance to survive a crash.

If we were to follow this infinite-mass object bs, one could say that a driver in a semi truck has a higher chance to die in a crash with a mini!!!??


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[ElectricMayhem]

As stated earlier, we were talking car vs car collision....which is generally the scope of the tests IIHS does.

Um, no.  IIHS crashes lots of cars into infinite mass non-deformable objects.  You should actually watch the videos sometime.

Someone called it "bs" above - all I can tell you is that if you get an education in the field, you will talk like that too.

(except technology...and older 50-60s car weighing the same as a new car will come out worse.)

Are you saying there are other, sometimes more important, factors?

And sure, saying "avoiding" the crash is easy.  But it rarely works out that way

Every single day, actually.  Most people with driving experience will tell you that, particularly if they ride a motorcycle.  It is very helpful to be able to stop quickly.  It is very helpful to have good emergency handling.

And no, car companies didn't go to lighter vehicle for safety.  The biggest motivator behind this was meeting CAFE and MPG targets.

I can tell you without question that reducing weight, especially unsprung weight, is very very high on the list of priorities.  One of my friends is a weight control engineer for Tesla - he makes US$200k so they must think it is important.  I am working on a 30 000 kg vehicle right now, and we are in a lot of trouble because it's 500 kg over the contract - we will have to write a cheque for 30 years' worth of electricity if we don't get the weight out, and there are axle weight issues as well.

[ElectricMayhem]

Most people in Alberta ride around in full size trucks that don't carry anything heavier or more substantial than the family pack of toilet paper from Costco.  Massive waste of manufacturing resources and fossil fuels.  I wonder of $2.00/L gas would have an impact?

Oh yes, $2.00 gas would solve an awful lot of problems.  Also, 8% car loans- there are all these $65k pickups in the driveways on my street, financed for 84 months at "zero" percent.  The buyers (they are really borrowers) are paying huge money to manufacturers and banksters, for very primitive vehicles.

[ElectricMayhem]

If we were to follow this infinite-mass object bs, one could say that a driver in a semi truck has a higher chance to die in a crash with a mini!!!??

Not exactly.  What I am saying is that if you are 100% going to hit the bridge abutment, or the tree, or the fixed-base utility pole, you want to be in the JCW, not the 18-wheeler with 30 000 kg of mass onboard, and not the 5 700 lb F-150.

Like I said, the energy to dissipate is m*v^2.   We are saying v is fixed, so the best thing to do is make sure the mass is as low as reasonably practicable.

[EV-Light]

If we were to follow this infinite-mass object bs, one could say that a driver in a semi truck has a higher chance to die in a crash with a mini!!!??

Not exactly.  What I am saying is that if you are 100% going to hit the bridge abutment, or the tree, or the fixed-base utility pole, you want to be in the JCW, not the 18-wheeler with 30 000 kg of mass onboard, and not the 5 700 lb F-150.

Like I said, the energy to dissipate is m*v^2.   We are saying v is fixed, so the best thing to do is make sure the mass is as low as reasonably practicable.

You being too simplistic about this...because you are not taking into account any other variables. If vehicles didn't have a crumple zone you'd be absolutely correct, but when you throw that in the calculation things rapidly change....bigger vehicles will typically be able to absorb a higher amount of energy generated by the impact because they have more areas to dissipate such energy.

 


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[Fobroader]

Most people in Alberta ride around in full size trucks that don't carry anything heavier or more substantial than the family pack of toilet paper from Costco.  Massive waste of manufacturing resources and fossil fuels.  I wonder of $2.00/L gas would have an impact?

Oh yes, $2.00 gas would solve an awful lot of problems.  Also, 8% car loans- there are all these $65k pickups in the driveways on my street, financed for 84 months at "zero" percent.  The buyers (they are really borrowers) are paying huge money to manufacturers and banksters, for very primitive vehicles.

HAHAHAHAHA....primitive vehicles?? What exactly is so primitive about a 4 door pickup truck that can do whatever some lame a$$ sedan couldn't dream of doing?? Is it the towing, the 4x4 capability, the hauling capacity or their popularity that irks you??

[Sir Osis of Liver]

The infinite mass barrier collision test replicates the forces involved of two identical cars hitting at identical but opposite speeds.
A JCW mini hitting the barrier at 30mph would experience the same forces as two JCW minis having a head on while they were each travelling at 30mph.

[Hannibalsmith]

The infinite mass barrier collision test replicates the forces involved of two identical cars hitting at identical but opposite speeds.
A JCW mini hitting the barrier at 30mph would experience the same forces as two JCW minis having a head on while they were each travelling at 30mph.

Should it be a mini hitting the barrier at 60 mph? The total energy of a mini hitting a barrier at 60 mph should be equivalent to the total energy of two minis travelling 30 mph hitting each other. Or am I missing something?

[rrocket]

As stated earlier, we were talking car vs car collision....which is generally the scope of the tests IIHS does.

Um, no.  IIHS crashes lots of cars into infinite mass non-deformable objects.  You should actually watch the videos sometime.

Someone called it "bs" above - all I can tell you is that if you get an education in the field, you will talk like that too.

(except technology...and older 50-60s car weighing the same as a new car will come out worse.)

Are you saying there are other, sometimes more important, factors?

And sure, saying "avoiding" the crash is easy.  But it rarely works out that way

Every single day, actually.  Most people with driving experience will tell you that, particularly if they ride a motorcycle.  It is very helpful to be able to stop quickly.  It is very helpful to have good emergency handling.

And no, car companies didn't go to lighter vehicle for safety.  The biggest motivator behind this was meeting CAFE and MPG targets.

I can tell you without question that reducing weight, especially unsprung weight, is very very high on the list of priorities.  One of my friends is a weight control engineer for Tesla - he makes US$200k so they must think it is important.  I am working on a 30 000 kg vehicle right now, and we are in a lot of trouble because it's 500 kg over the contract - we will have to write a cheque for 30 years' worth of electricity if we don't get the weight out, and there are axle weight issues as well.

I work in the industry, so it's not like I fell out of a turnip truck yesterday.  I also race and ride motorcycles, cars, etc.  So in goes without saying that avoiding accidents is best.  But it doesn't always work out that way.  The number of road deaths in NA per year confirms this.

Mass will generally win the war.  I've read far too many papers from the IIHS, SAE, NHTSA, etc that agree with that statement.  My position is the same as theirs...mass will usually win.  I'll not bother listing them.  They are readily available online if you're motivated to look for them.

And yes, lightness is important.  But as previously stated, it has more to do with fuel economy goals than with safety.  As with the 30k KG vehicle you're working on...the 500kg isn't an issue for safety sake...it's an issue for electricity usage.

[ElectricMayhem]

Look, I'm not going to make any more posts except to say this:

Mass is just that, mass.  Mass does not equal safety.  If mass equaled safety, the 1988 Delta 88 would be one of the safest cars on the road.

You might think that m*v^2 is abstruse egghead engineering, but you can understand most of what you need to know from that energy figure.  Yes, the details of the crash energy dissipation arrangement matter too, but not as much as that figure of merit.  If you ask an accident investigator what are the first things he wants to know, the mass and the velocity are very high on the list.

You can say that you are better off buying more fuel to buy a heavier vehicle than the JCW, and you would not be wrong.  All I am saying is that you should strike a balance.  When you are buying an F-150, you are buying a vehicle that is going to plow straight ahead in the half-second when you want it to yaw sharply to avoid an accident.  So maybe look at something lighter.  You may dismiss this type of thinking now, but you will wish you listened when you have your accident.

There are also issues with the high CofG of something like an F-150, particularly the ones with the popular six inch lift kits.  Yes, engineers are saving you to some extent from rollovers through clever electronics and software, but there are fundamental principles of physics that bear directly on why you don't really want to be in such a vehicle.

I am fully aware that there are a lot of people who think pickups are highly sophisticated and worth a lot of money.  There has been a lot of very successful marketing in that regard.  Manufacturers are making around $20k on the King Ranch type pickups, so there a lot of reasons for them to prosecute the ad campaigns which haven't changed much since the "Like a rock" era.

I am not saying you shouldn't have freedom to buy a pickup if that is what you want.  But certain truths have been obtained through over a hundred years of vehicle engineering, and you can't say nobody told you about them.

Me, when I need a pickup I rent a 3/4 ton one for $55/day.  You may find that might work for you too.  It is not that I can't afford a pickup, because I make a good living as a driverless vehicle engineer. It's just that it is hard for me to justify spending $1800 more per year on fuel compared to my S4 Avant daily driver.  I only need a pickup about twice a year, and I suspect most suburban people would come to that conclusion too, upon sober analysis.

[rrocket]

^^I too am on the "pickup trucks suck" bandwagon.  I prefer more car-like trucks if I ever needed one (Honda Ridgeline).

I prefer sports cars and luxury cars.

SUVs. CUVs, Trucks, Minivans?  No bueno.

[johngenx]

 Is it the towing, the 4x4 capability, the hauling capacity or their popularity that irks you??

Things that are used by a small percentage of truck owners.