6 ms·

This is great video to study on many levels beyond self-driving car. Some observations: * The car behind didn't show turn signal so probably driver wasn't payi

by sytelus 10y ago

This is great video to study on many levels beyond self-driving car. Some observations: * The car behind didn't show turn signal so probably driver wasn't paying attention. * A small car escaping with not too much damage while SUV rolls over many times * From physics point of view, the car behind produced almost perfect torque that started horizontal spin on SUV * Collisions with barrier at high speed can produce lots of rolls. Many time we see cars upside down in accident and wonder how did that happened. This is how. * The middle barrier did its job wonderfully even against massive inertia of SUV. Cars on other side remained unscathed!

sumedh 10y ago
> Many time we see cars upside down in accident and wonder how did that happened. This is how Living in India, I have seen a fair share of accidents where the car is upside down. I always used to wonder how that happens, now I know.
- sjs382 10y ago
  It's also "a thing" in New Orleans. Check this out: https://www.reddit.com/r/NewOrleans/search?q=flip&sort=new&restrict_sr=on https://www.reddit.com/r/NewOrleans/search?q=flip&sort=new&r...
gingerlime 10y ago
I'm feeling rather dumb, but can't really intuitively understand the physics here. I see a small car hitting a pretty huge one and yet spins the huge one several times. I always thought those bigger cars are safer / stronger / more resistant to hits? Is it purely because it hit it at the corner, so all the force went into the "spinning axis"? (did I say I feel dumb?)
- Paradigma11 10y ago
  The way i see it the small car just got the SUV to ram the middle barrier. The spinning momentum resulted from that crash and facing normal to the dominant moving direction.
- agumonkey 10y ago
  SUV center of mass is probably higher and easier to tilt. Both cars braking, center of mass shifting toward their front and lowering. Meaning the small car momentum was peak at the collision point, while the SUV rear end was already lifted thus lighter. Direction of the collision helped transfer the energy into torque. The barrier provided the final help to start the car tumbles.
- rdslw 10y ago
  Look on two things: A) main that SUV happened (just before starting sommersaults) to position itself orthogonal to its previous way of moving. In this position all wheels of SUV created massive 'resistance' to continue move forward B) it happened partialy because of the middle barrier. WOuld it be missing, SUV would probably move (on the arc) without sommersaults. Change of orientation was caused by small car, but look that up to moment A) SUV more less was moving fine.
- zo1 10y ago
  The SUV had forward momentum, yet it was suddenly facing sideways due to the side-back impact from the smaller vehicle. That means the tires were skidding and "gripping" the car at the base rather than "rolling", while the whole body wanted to go forward. Hence, it toppled and kept rolling because there was nothing to stop it.
- fragmede 10y ago
  > I always thought those bigger cars are safer / stronger / more resistant to hits? Physics would have you start with a spherical, uniformly dense car, but cars aren't that. Crumple zones engineered for passenger safety requirement mean that intuition falls short unless you really dig into it and add stuff like center of gravity to the model. Also think about why you believe that - looks can be deceiving, and marketing, especially for rare expensive purchases like cars, very much plays on emotional appeal rather than actual science. ("Ultimate driving machine"? Pft, really?). The original SUVs were designed off truck platforms and did quite poorly in safety tests, and their higher center of gravity doesn't help at all. (Though it looks like a minivan in the video.) Just like two objects falling will fall at different speed in the real world due to air resistance, bigger != better with cars. You can't see crumple zones just by looking at how pretty the car is; vehicle safety is one area where government regulation has made cars safer by requiring all new cars sold in the US to meet a very high safety bar, and that's improved over the years, evident in this video of an intentional crash between a 1962 Cadillac vs a 2002 model. https://youtu.be/O-WYKYrq5FI https://youtu.be/O-WYKYrq5FI
- Waterluvian 10y ago
  Take two cereal boxes. Put one flat and the other on its end. Smack the flat one into the tall one. Which one begins to roll? This is severely exaggerated but you get the idea of what's happening between the car and SUV.
- Tloewald 10y ago
  The SUV would have spun if it didn't hit the crash barrier.
- sytelus 10y ago
  Torque is r X F meaning that small force applied over a long length can produce huge torque! You can move a huge rock if you use a long enough metal stick for leverage. This is why Archimedes said, Give me a lever long enough and a fulcrum on which to place it, and I shall move the world. Large angular acceleration due to large torque is then directly result of Euler's equations.
brodie78382 10y ago
> The car behind didn't show turn signal Watch the video again; the little red car turns on their blinker and does a very slow shift to the right before clipping that stopped SUV. You're right that he wasn't paying attention, but his reaction time is incredibly slow - it looks like that car had just enough time to slam on their brakes or swerve to the right, yet they did neither.
- AznHisoka 10y ago
  not sure what the speeds these cars were traveling at but assuming this is regular highway speed is slow reaction time really a good excuse? aren't you supposed to have a wide enough space between you and the car in front of you? to compensate for any slowness in reaction.
  - hobbes78 10y ago
    If it's any indication, you can read 113 km/h on the dashcam overlay. Besides, the Opel Corsa, at least for the few seconds before the crash, seems to roughly maintain the same distance from the Tesla, so it should be travelling at a very similar speed...
- agumonkey 10y ago
  It's odd that the turn signal is only located at the top of the car. I guess the mid height one was broken ? I think the situation is not entirely unclear, it seemed that there was a problem ahead of the SUV, that made a bunch of cars slow down altogether. I still don't understand the smaller red car driver decisions.. maybe he didn't know what to do and hesitated and tried to swerve as a last resort. Or maybe he was just not watching. The SUV break lights were on quite a long time..
  - bcraven 10y ago
    It looks like a 2001 Vauxhall Corsa, that is just where the indicators are.
    - 10y ago
79d697i6fdif 10y ago
The biggest thing I noticed was just how easily SUV's flip over. This has been a problem forever I'm just surprised that regulators don't take more notice of it. Rollovers are far more likely to result in injury or death. Most cars just don't flip, all the traction their tires have is simply not enough to do it on flat ground. Yeah anything could flip over once you go off the road but the SUV in this looks like a rolling death machine.
- devy 10y ago
  That also depends on the momentum (weight ratio, impact speed angle, etc.) The lesser the weight, the worst off during impact - we've seen that too often in NHTSA crash tests.
  - marcosdumay 10y ago
    Flipping depends entirely on geometry. SUVs have high suspension, have a lot of weight at their top, and have an overall higher height to width ratio. Also, their aerodynamics do not push as much down as on lower cars.
- Gravityloss 10y ago
  I've seen a crash that was very similar. A tiny car hit the rear bumper of a SUV, on the right half, not really even a hard hit. The SUV got turned to the left and hit the slightly raised center of the road (maybe 10 cm high?) and spun and slid on its roof. Everybody was okay in the end.
- glenntzke 10y ago
  I was in a very bad accident when a GMC pickup t-boned my 98 Subaru Impreza 2.5RS at ~55mph. My car crumpled and was totaled but took the hit and went for a 4 wheel slide across the road. A nice balanced car takes hits really well. And I'm very glad I wore my seatbelt.
- cylinder 10y ago
  Because people think these SUVs are "safer" due to their size. And then it becomes an arms race; you see the highway full of large SUVs, and you feel vulnerable in a tiny compact car, because you think they will crush you in a collision, so others start buying SUVs to "protect" themselves. These land-beasts might be comfortable but they are unsafe, take an excess and unfair amount of space on the road, consume too much fuel, and trigger arms race. They need to be regulated to death for most users.
Tloewald 10y ago
The SUV was pushed into the crash barrier and small car wasn't, so it's a highly unfair comparison. We did a lot of safety research before buying our current round of cars, and you need to not generalize about cars based on classifications like "SUV". Look at actual data from actual cars on actual roads, e.g. http://www.iihs.org/iihs/topics/driver-death-rates http://www.iihs.org/iihs/topics/driver-death-rates Note that you can find vehicles like the Honda Pilot that are enormously popular and have in effect ZERO fatalities. What's horribly unsafe to everyone is passenger cars built on truck frames.
- loeg 10y ago
  > What's horribly unsafe to everyone is passenger cars built on truck frames. Have any examples? The vast majority of new SUVs (which the one in this incident appears to be) are unibody rather than body-on-frame ("truck frame" style).
  - Animats 10y ago
    Other than the Jeep Wrangler, few car-size vehicles are still built on truck frames. About 10% of SUVs still are, mostly the larger ones.
  - pacificmint 10y ago
    > Have any examples? The vast majority of new SUVs [...] are unibody rather than body-on-frame Apparently there are 18 models of Body-On-Frame SUVs that are being sold in the US in 2016: Cadillac Escalade Cadillac Escalade ESV Chevrolet Suburban Chevrolet Tahoe Ford Expedition GMC Yukon GMC Yukon XL Infiniti QX80 Jeep Wrangler Land Rover LR4 * Lexus GX460 Lexus LX570 Lincoln Navigator Mercedes-Benz G-Class Nissan Armada Toyota 4Runner Toyota Land Cruiser Toyota Sequoia Source: http://www.goodcarbadcar.net/2016/02/body-on-frame-suv-production-2016-model-year-north-america.html http://www.goodcarbadcar.net/2016/02/body-on-frame-suv-produ...
    - brianwawok 10y ago
      Those are mostly the biggest ones. Maybe 25% of market at best?
Infernal 10y ago
I'm not sure what you mean by "the car behind didn't show turn signal". If you're referring to the pink hatchback that ultimately rear-ended the SUV - the pink hatchback seems to be making a lane change to the right after passing. The driver seems to have signaled and looked to the right to clear his/her blindspot at the same moment the SUV ahead slams on the brakes. It really seems like bad luck, that traffic would suddenly stop at the exact moment the driver of the pink hatchback looks to the right to change lanes.
- seletz 10y ago
  Well no -- that wasn't bad luck at all. He simply was way too close for the speed. Back in the day when I got my driver's license we were told to have 3 seconds of distance. One second to react one second to brake and one second for safety, if I remember correctly.
  - slavik81 10y ago
    Around here they recommend 2s. As part of a science fair project, I measured the following distance of cars on a nearby highway. It's been about 15 years but IIRC, the mode was ~0.5s.
- lb1lf 10y ago
  > It really seems like bad luck, that traffic would suddenly stop at the exact moment the driver of the pink hatchback looks to the right to change lanes. -Pet peeve of mine: "Bad luck" is incredibly rare in traffic. This accident occurred because the hatchback was too close to the car in front of it; not because of bad luck.
- rackbreaker 10y ago
  At 0:00 the pink hatchback is well behind the car it's trying to pass. At 0:02 the brake lights of the SUV illuminate; the pink hatchback is still not quite caught up to the car it's trying to pass. Instead of braking, the hatchback keeps accelerating trying to beat the closing gap. No signaling at any time. Looks much more like bad judgment than bad luck.

by sytelus 10y ago

sumedh 10y ago

> Many time we see cars upside down in accident and wonder how did that happened. This is how Living in India, I have seen a fair share of accidents where the car is upside down. I always used to wonder how that happens, now I know.

sjs382 10y ago
It's also "a thing" in New Orleans. Check this out: https://www.reddit.com/r/NewOrleans/search?q=flip&sort=new&restrict_sr=on https://www.reddit.com/r/NewOrleans/search?q=flip&sort=new&r...

gingerlime 10y ago

I'm feeling rather dumb, but can't really intuitively understand the physics here. I see a small car hitting a pretty huge one and yet spins the huge one several times. I always thought those bigger cars are safer / stronger / more resistant to hits? Is it purely because it hit it at the corner, so all the force went into the "spinning axis"? (did I say I feel dumb?)

Paradigma11 10y ago
The way i see it the small car just got the SUV to ram the middle barrier. The spinning momentum resulted from that crash and facing normal to the dominant moving direction.
agumonkey 10y ago
SUV center of mass is probably higher and easier to tilt. Both cars braking, center of mass shifting toward their front and lowering. Meaning the small car momentum was peak at the collision point, while the SUV rear end was already lifted thus lighter. Direction of the collision helped transfer the energy into torque. The barrier provided the final help to start the car tumbles.
rdslw 10y ago
Look on two things: A) main that SUV happened (just before starting sommersaults) to position itself orthogonal to its previous way of moving. In this position all wheels of SUV created massive 'resistance' to continue move forward B) it happened partialy because of the middle barrier. WOuld it be missing, SUV would probably move (on the arc) without sommersaults. Change of orientation was caused by small car, but look that up to moment A) SUV more less was moving fine.
zo1 10y ago
The SUV had forward momentum, yet it was suddenly facing sideways due to the side-back impact from the smaller vehicle. That means the tires were skidding and "gripping" the car at the base rather than "rolling", while the whole body wanted to go forward. Hence, it toppled and kept rolling because there was nothing to stop it.
fragmede 10y ago
> I always thought those bigger cars are safer / stronger / more resistant to hits? Physics would have you start with a spherical, uniformly dense car, but cars aren't that. Crumple zones engineered for passenger safety requirement mean that intuition falls short unless you really dig into it and add stuff like center of gravity to the model. Also think about why you believe that - looks can be deceiving, and marketing, especially for rare expensive purchases like cars, very much plays on emotional appeal rather than actual science. ("Ultimate driving machine"? Pft, really?). The original SUVs were designed off truck platforms and did quite poorly in safety tests, and their higher center of gravity doesn't help at all. (Though it looks like a minivan in the video.) Just like two objects falling will fall at different speed in the real world due to air resistance, bigger != better with cars. You can't see crumple zones just by looking at how pretty the car is; vehicle safety is one area where government regulation has made cars safer by requiring all new cars sold in the US to meet a very high safety bar, and that's improved over the years, evident in this video of an intentional crash between a 1962 Cadillac vs a 2002 model. https://youtu.be/O-WYKYrq5FI https://youtu.be/O-WYKYrq5FI
Waterluvian 10y ago
Take two cereal boxes. Put one flat and the other on its end. Smack the flat one into the tall one. Which one begins to roll? This is severely exaggerated but you get the idea of what's happening between the car and SUV.
Tloewald 10y ago
The SUV would have spun if it didn't hit the crash barrier.
sytelus 10y ago
Torque is r X F meaning that small force applied over a long length can produce huge torque! You can move a huge rock if you use a long enough metal stick for leverage. This is why Archimedes said, Give me a lever long enough and a fulcrum on which to place it, and I shall move the world. Large angular acceleration due to large torque is then directly result of Euler's equations.

brodie78382 10y ago

> The car behind didn't show turn signal Watch the video again; the little red car turns on their blinker and does a very slow shift to the right before clipping that stopped SUV. You're right that he wasn't paying attention, but his reaction time is incredibly slow - it looks like that car had just enough time to slam on their brakes or swerve to the right, yet they did neither.

AznHisoka 10y ago
not sure what the speeds these cars were traveling at but assuming this is regular highway speed is slow reaction time really a good excuse? aren't you supposed to have a wide enough space between you and the car in front of you? to compensate for any slowness in reaction.
- hobbes78 10y ago
  If it's any indication, you can read 113 km/h on the dashcam overlay. Besides, the Opel Corsa, at least for the few seconds before the crash, seems to roughly maintain the same distance from the Tesla, so it should be travelling at a very similar speed...
agumonkey 10y ago
It's odd that the turn signal is only located at the top of the car. I guess the mid height one was broken ? I think the situation is not entirely unclear, it seemed that there was a problem ahead of the SUV, that made a bunch of cars slow down altogether. I still don't understand the smaller red car driver decisions.. maybe he didn't know what to do and hesitated and tried to swerve as a last resort. Or maybe he was just not watching. The SUV break lights were on quite a long time..
- bcraven 10y ago
  It looks like a 2001 Vauxhall Corsa, that is just where the indicators are.
  - 10y ago

79d697i6fdif 10y ago

The biggest thing I noticed was just how easily SUV's flip over. This has been a problem forever I'm just surprised that regulators don't take more notice of it. Rollovers are far more likely to result in injury or death. Most cars just don't flip, all the traction their tires have is simply not enough to do it on flat ground. Yeah anything could flip over once you go off the road but the SUV in this looks like a rolling death machine.

devy 10y ago
That also depends on the momentum (weight ratio, impact speed angle, etc.) The lesser the weight, the worst off during impact - we've seen that too often in NHTSA crash tests.
- marcosdumay 10y ago
  Flipping depends entirely on geometry. SUVs have high suspension, have a lot of weight at their top, and have an overall higher height to width ratio. Also, their aerodynamics do not push as much down as on lower cars.
Gravityloss 10y ago
I've seen a crash that was very similar. A tiny car hit the rear bumper of a SUV, on the right half, not really even a hard hit. The SUV got turned to the left and hit the slightly raised center of the road (maybe 10 cm high?) and spun and slid on its roof. Everybody was okay in the end.
glenntzke 10y ago
I was in a very bad accident when a GMC pickup t-boned my 98 Subaru Impreza 2.5RS at ~55mph. My car crumpled and was totaled but took the hit and went for a 4 wheel slide across the road. A nice balanced car takes hits really well. And I'm very glad I wore my seatbelt.
cylinder 10y ago
Because people think these SUVs are "safer" due to their size. And then it becomes an arms race; you see the highway full of large SUVs, and you feel vulnerable in a tiny compact car, because you think they will crush you in a collision, so others start buying SUVs to "protect" themselves. These land-beasts might be comfortable but they are unsafe, take an excess and unfair amount of space on the road, consume too much fuel, and trigger arms race. They need to be regulated to death for most users.

Tloewald 10y ago

The SUV was pushed into the crash barrier and small car wasn't, so it's a highly unfair comparison. We did a lot of safety research before buying our current round of cars, and you need to not generalize about cars based on classifications like "SUV". Look at actual data from actual cars on actual roads, e.g. http://www.iihs.org/iihs/topics/driver-death-rates http://www.iihs.org/iihs/topics/driver-death-rates Note that you can find vehicles like the Honda Pilot that are enormously popular and have in effect ZERO fatalities. What's horribly unsafe to everyone is passenger cars built on truck frames.

loeg 10y ago
> What's horribly unsafe to everyone is passenger cars built on truck frames. Have any examples? The vast majority of new SUVs (which the one in this incident appears to be) are unibody rather than body-on-frame ("truck frame" style).
- Animats 10y ago
  Other than the Jeep Wrangler, few car-size vehicles are still built on truck frames. About 10% of SUVs still are, mostly the larger ones.
- pacificmint 10y ago
  > Have any examples? The vast majority of new SUVs [...] are unibody rather than body-on-frame Apparently there are 18 models of Body-On-Frame SUVs that are being sold in the US in 2016: Cadillac Escalade Cadillac Escalade ESV Chevrolet Suburban Chevrolet Tahoe Ford Expedition GMC Yukon GMC Yukon XL Infiniti QX80 Jeep Wrangler Land Rover LR4 * Lexus GX460 Lexus LX570 Lincoln Navigator Mercedes-Benz G-Class Nissan Armada Toyota 4Runner Toyota Land Cruiser Toyota Sequoia Source: http://www.goodcarbadcar.net/2016/02/body-on-frame-suv-production-2016-model-year-north-america.html http://www.goodcarbadcar.net/2016/02/body-on-frame-suv-produ...
  - brianwawok 10y ago
    Those are mostly the biggest ones. Maybe 25% of market at best?

Infernal 10y ago

I'm not sure what you mean by "the car behind didn't show turn signal". If you're referring to the pink hatchback that ultimately rear-ended the SUV - the pink hatchback seems to be making a lane change to the right after passing. The driver seems to have signaled and looked to the right to clear his/her blindspot at the same moment the SUV ahead slams on the brakes. It really seems like bad luck, that traffic would suddenly stop at the exact moment the driver of the pink hatchback looks to the right to change lanes.

seletz 10y ago
Well no -- that wasn't bad luck at all. He simply was way too close for the speed. Back in the day when I got my driver's license we were told to have 3 seconds of distance. One second to react one second to brake and one second for safety, if I remember correctly.
- slavik81 10y ago
  Around here they recommend 2s. As part of a science fair project, I measured the following distance of cars on a nearby highway. It's been about 15 years but IIRC, the mode was ~0.5s.
lb1lf 10y ago
> It really seems like bad luck, that traffic would suddenly stop at the exact moment the driver of the pink hatchback looks to the right to change lanes. -Pet peeve of mine: "Bad luck" is incredibly rare in traffic. This accident occurred because the hatchback was too close to the car in front of it; not because of bad luck.
rackbreaker 10y ago
At 0:00 the pink hatchback is well behind the car it's trying to pass. At 0:02 the brake lights of the SUV illuminate; the pink hatchback is still not quite caught up to the car it's trying to pass. Instead of braking, the hatchback keeps accelerating trying to beat the closing gap. No signaling at any time. Looks much more like bad judgment than bad luck.