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Sunday, February 25, 2007

An analytical challenge: Predict Trajectory

If you like crime scene investigation, or reverse engineering or just analyzing things, here’s a nice challenge for you.

Accent car accident Kodapur Madhapur Hyderbad
About a week ago, during my morning walk, I found a car (Hyundai Accent) turned upside down on a two lane road between Madhapur and Kondapur, in Hyderabad India.

Unlike other accidents one might have seen, this scene was a bit peculiar. Usually, an accident happens when a vehicle hits another vehicle or hits other objects near the road (like hitting a tree, falling into a pit etc). But this particular accident was different because of following reasons:
car accident Kodapur Madhapur Hyderbad

The front and the rear end of the vehicle were almost undamaged, meaning the car was not hit by other vehicles, either in front or from back

The road divider (median) is intact. Meaning, the vehicle has not hit the median.

Thus, this is a case of speed, negligent and most probably drunken driving and the accident has happened without involving any other vehicle on the road.

Now, coming to the question, can you predict the trajectory this vehicle would have taken before overturning itself?
car accident Kodapur Madhapur Hyderabad
What might have triggered this? Did the vehicle tipped over a stone while cruising at top speed? (My flat mate Prasad feels this one is the most probable reason).

In the picture at your right, you can make out the radiator water spilled out, indicating vehicle has rotated a bit on its vertical axis before coming to halt
car accident Kodapur Madhapur Hyderabad

In the second pic you can see some grass. I'm not sure if the car dragged it along or it came there by other means (people placing it there or by wind etc). There're no trees (of that particular type of leaf) with branches hanging so low for a car to grab it.

The car has not dragged further after turning over and hence the passengers were saved (seatbelt should have done its job, no blood was found at the site). Had the vehicle dragged further, it would have squeezed passengers to death.
car accident Kodapur Madhapur Hyderbad
What made this car to spin exactly 180 degrees on its horizontal axis (clockwise)?

---Acknowledgments---
Data Transfer courtesy: Prasad.
Photos taken using: SE K750i

15 comments :

hari said...

I've seen something like this myself on a few highways.

Always wondered how they managed it. In fact, I once saw a car caught right between a stone median bang in the middle of the city.

Wonder how drivers accomplish such feats.

Sandesh said...

If you've seen any Bond movies(Even the latest, Casino Royale) you get to see such incidents where the make the car upside down! This might be one such incident!

Shrinidhi Hande said...

@ Hari: :)

@ Sandesh:
Movies are different. There a stunt is done under controlled condition using invisible wires and other mechanisms by professional stunt experts. I dont think this scene was made for a movie...

Anonymous said...

isnt it so cool?
its kind of scary also.but i think the driver is very careless!

logesh tamilselvan said...

I dont think any of the Hyundai accent models has AIRBAGS..
Still the passengers are not injured..sounds great! really very lucky!

i guess..the car must have jumped at very good height or hit badly in a stone or pavement and got upset.. coz the rear wheel Rim's(in the first two pic's) are slightly collapsed

Nice work shrinidhi! Interesting post and Pic's!
Anyway feel sad for the car owner! :p

Shrinidhi Hande said...

@ Anonymous: Thanks 4 the comment

@ Logesh: Thanks for that extended analysis. Accent doesn't have airbag as standard fittment, agreed

The possibilities you have mentioned cant be ruled out

Thanks for the complements

Jubin George said...

This assumption is based on thinking that it rotated anti-clockwise, not clockwise as you said, in its horizontal axis, and rotating 360 degrees on its vertical axis clockwise, that caused the car not to drag forward much on its roof.

If it actually had rotated in clockwise direction in its horizontal axis, and turned only a bit (if it's not 360, it has turned in anti-clockwise) in its vertical axis, the following theory is completely wrong.

Its rear right wheel hit a stone or the divider, and the driver impulsively steared to the left, and then to the right seeing the car going to move diagonally across the road - making it move back to right in a curve. Hitting the stone/divider must have caused the car's right side to lift a bit too, and when it's added with the centripetal push, it got toppled. It fell right on the roof, the hood hit on the road and lifted up, not leaving a mark on the road when it turned in its vertical axis. The car doesn't seem to have been in the air, and must have almost rolled upside down, and that could be the reason that its roof is not completely collapsed in. I also think the drivers seat had fell backwards to save his/her life.

The point the vehicle hit the stone/divider will be 100-150 mtrs before the spot it's now. And the car would have been 160+ kmph when hit.

Shrinidhi Hande said...

Thanks for the detailed analysis Jubin george... Wish we could recreate the problem under controlled conditions...

Gaurav Sethi said...

Hi Shrinidhi,

Here is what I think might have happened :
My hypothesis is that the accident occurred at night (1) when the drunk (2
)
driver hit the road divider (3) on its right rear wheel (4) and the car flipped over sideways (4) to fall the way it has in this case.


This is supported by the following observations :


1. The accident occurred at night. The pics seem to be taken in the early morning (my guess, nidhi will have to confirm). Because the shadows are more horizontal so its either early morning or late evening, but I will rule out evening because there is usually more traffic at that time.


2. There has been no collision with any other vehicle. This kind of accident would have made a big dent on the car which is not present. (as observed by you).

So the probability of the driver being drunk becomes very high as that is the most common cause of accidents.


3. If we look carefully at the leaves under the car the only place they are present are on the trees on the divider. (look at the pics.) So the car definitely hit the divider.

The leaves could not have come from the trees on the other side of the road as that would be too far.

The leaves/branches got stuck on the roof when the car was flipping.

4. It is visible in the photos that there is a dent on the right rear wheel, so that is probably where the car hit the divider.

5. When the rear tyre of the car hit the divider, the car tended to fall towards the divider but the driver made desperate measures to balance the car by turning the wheels towards the left. However, this led to again loss of balance and the car tripped horizontally 180' clockwise to fall upside-down on the road.

I would also like to add a paint image of the events of the accident but we cant add attachments to the comments. However being a nonengineer I think I can better explain point 5 by drawing rather than action of forces.

This was posted an year ago but hope this makes sense because this would contradict the assertion by Jubin George.

Shrinidhi Hande said...

Hi Gaurav,

Thanks for the comment...

If you wish to send a drawing depicting the solution please send it to admin at enidhi dot net... I will include it in the post with due credits to you.

1. You can see the timing in the photo... Also as stated in the post the pics were taken during morning walk. Accident has happened during the night.

2. Correct

3. Most probably right.. I should have taken photo of the divider to assess damage to it, if any... My mistake..

4. I agree with that possibility

5. I appreciate your visualization- but what do you think made the car jump high in the air that rear wheel went high enough to hit the road divider? Something should have abruptly tossed the car above ground.. Any guess?

nakul_chandigarh said...

i hav actually gone through a similar accident where my car also flipped 180degrees! so i guess i can add a little to the above analysis....
As the accident took place late at night thus the car showed no signs of damage from front or rear..
and as for my observation it hasn't even hit any divider's because none of the tyre's seem to be flat. because wen a car hits the divider at a high speed the tyres burst out almost immediately...
as for my guess the car should be well above 100 kmph and there should have been fine gravel or sand on the road (as in my case).
the person tried to turn the car or tried to move the car very abruptly or was tryin to avoid someone else on the road..
thus could not control the car at that high speed!
the car they swayed (as Accent is a front wheel driven vehicle) and due to force finally flipped...
the road should have had skid marks too...

Shrinidhi Hande said...

@ Nakul,

yes none of the tyres were flat, think I afree on that divider part...

Yes, the place has a slightly sharp turn (30 degrees probably)

Thanks for sharing your thoughts and thank god nothing happened to you when your car tilted...

Anonymous said...
This comment has been removed by a blog administrator.
Subbu said...

Car should have fallen from loaded truck which use to carry cars.


Thanks
Subbu

Shrinidhi Hande said...

Possible...