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Old 26th May 2013, 23:54   #1
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Default Airbags deployed after hitting a dog. Understanding why?

Hey Folks, to kill the suspense upfront if you are wondering why it was an unfortunate pleasure then the answer is that lucky for me there was not much harm done to me the sole occupant in the car or any human on the road, resulting in experiencing airbag deployment which otherwise would be in a pretty grim situation.

Now without giving away all the ending let me give you the story. My work entails me to travel internationally once in a while and this time it took me to Israel which is one the biggest hitech company hubs outside of Bay area and Bangalore. Actually I have been visiting Israel pretty often (3rd time in 1.5yr) since my semiconductor company has multiple design and development offices based there. Since I usually need to move between different offices and love to drive, I rent and drive on my own. Driving is very easy as its like US (right hand side) in terms of roads and cars and having lived in US for a while it comes easily to me.

The incident happened at end of of my trip when time I was driving from south of Israel towards Ben Gurion INtl Airport in Tel Aviv which was about 100kms from the city i was in. My flight was at 6am and I checked out at 1am since its about an hour's drive to the airport thanks to the amazing highways where averaging 120kmph is piece of cake (legal limit is 110kmph). I was driving a Mazda3 fully loaded (front/curtain airbags, abs, esp etc). I had just gotten out of the city and hit the highway doing about 90kmph on the slower lane. Eventually I came across a truck and I slowed down and moved to the fast lane to overtake hitting about 80kmph and gradually gaining speed. This part of the highway had street lights and was well lit. As i started overtaking the truck and almost came in parallel I noticed a reasonably big dog possibly wild came and stood in front of the truck. Within that split second I remem thinking to myself that please dont cross and come into my lane. And that very moment the dog noticed the truck and for some reason rather than sprinting he just ran slowly across into my lane. It was almost as if he was just saving himself from the truck and didnt notice my car. I braked the moment he moved but there was not much I could do due to limited distance. Since truck was in parallel on the right and railing on the left hand side i just held the steering and didnt steer the car sideways and rammed into the dog.

Next thing I know there is this huge blast or pop, my chest feel crushed and ears are ringing and the car is full of smoke. I was in a bit of shock and took me a second or so to realize that the air bags have deployed both for me and the passenger side. The reason my chest was crushed was cause of the pre-tensioners in the seat belts which kicked along with the air bags. Once i got my senses back I immediately opened the windows to release the smoke and turned on the hazard sign since i was stationery on the fast lane of the highway and got out of car to ensure I dont get rammed by someone from the back. Lucky for me I had kept my foot on the brake and the car stuck to the lane. Since it was past 1 am, traffic was light and the highway was well lit and helped avoid any further incidents from the traffic coming from behind. I inspected the damage and suspecting the worst only to find a broken number plate and rest of the bumper almost intact. At that very moment i realised that the engine was still running and I immediately jumped in and moved the car to safety on the right side off the road.

To cut rest of the story short. I took 5 mins sitting in the car calming myself. Inspected the car for damage and decided it made most sense to drive onto the airport without airbags or seat belts if i wanted to catch my flight and be back in India. I reached airport without any further incidents but I drove very cautiously. I had full insurance and Avis was very helpful. Checked with me for any personal injury and then immediately made an incident report and let me on my way to catch the flight without any liability.

Now coming to the questions and doubts. Please look at the 3 pics I managed to take below.

Airbags deployed after hitting a dog. Understanding why?-20130524_012006_tbhp.jpg
Airbags deployed after hitting a dog. Understanding why?-20130524_011954_tbhp.jpg
Airbags deployed after hitting a dog. Understanding why?-20130524_023049_tbhp1.jpg

You can see the airbags deployed and then the last pic of the cars front. You can easily notice the broken number plate and the bumper broken mount for the plate. But beyond that there is hardly any visible damage. There was some damage on the lower side of the bumper to the grill but that's about it. There is not even any misalignment of the bumper. Was this hit strong enough to trigger the airbags or maybe the sensors were calibrated too sensitive? I understand that airbags are for frontal impact in case of a crash which is strong enough to cause lot of damage and energy transfer inside the car to the occupants. But a 1200kg car hitting a 30kg dog doesnt seem like that event to me.

This makes me feel a bit concerned cause I have a Figo with airbags and hitting a dog on Indian highways is not unlikely . Will like to hear inputs from folks on the forum. I have written an email to Mazda, lets see whether I get a response from them.

Last edited by supertinu : 27th May 2013 at 00:01.
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Old 27th May 2013, 00:31   #2
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Default re: Airbags deployed after hitting a dog. Understanding why?

One important point to note is that airbag deployment does not depend on impact intensity alone. It also depends on rate of deceleration. The airbag controller does not know that you hit a dog. It just sensed high rate of deceleration and then an impact and it did what it was programmed to do. Deploy air bags.
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Old 27th May 2013, 06:56   #3
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Default re: Airbags deployed after hitting a dog. Understanding why?

Looks like the car hardly took a hit. I'm quite surprised the airbags deployed. I could be wrong but in not-so-expensive cars like the Mazda3 I don't the electronics are configured to calculate deceleration etc. for airbag deployment. Its only sensor based.

The bumpers in most cars today are very flexible so there is a good chance the bumper deformed quite a bit hence activating the sensors before returning back to normal.

Aren't sensors usually placed behind a metal sub-frame? So the sensors don't get activated until the sub-frame has actually taken a hit causing a more permanent damage?
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Old 27th May 2013, 07:18   #4
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Default re: Airbags deployed after hitting a dog. Understanding why?

Doesn't matter if the car is expensive or cheap. All airbag systems calculate rate of deceleration for airbag deployment.

Edit: Read the section 'How Airbags Work' on the Wikipedia article below.

http://en.m.wikipedia.org/wiki/Airbags

Last edited by vikram_d : 27th May 2013 at 07:23.
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Old 27th May 2013, 07:58   #5
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Default re: Airbags deployed after hitting a dog. Understanding why?

I too think that you tried too hard to save the dog and stood on the brake. This should have triggered the sequence. The same braking force and impact can also happen if you narrowly missed being crushed by a trailor because you managed to stop in time, but hit it slightly (The airbag system does not have eyes !!) with can equate to a 30Kg dog as you mentioned.It detected just frontal impact and no roll over so the side curtain airbags did not deploy.
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Old 27th May 2013, 08:47   #6
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Default re: Airbags deployed after hitting a dog. Understanding why?

Quote:
Originally Posted by flipsyde View Post
Looks like the car hardly took a hit. I'm quite surprised the airbags deployed. I could be wrong but in not-so-expensive cars like the Mazda3 I don't the electronics are configured to calculate deceleration etc.
Inexpensive Mazda uses the same SRS airbags used in the Expensive Merc C class and the airbag deployment algorithms are standard across SRS, though the number of sensory inputs can wary.

OT, just wanted to know what happened to the dog.Since the damage to the Mazda's bumper was negligible, does that mean that the dog took the major impact ?
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Old 27th May 2013, 09:09   #7
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Default re: Airbags deployed after hitting a dog. Understanding why?

Good to hear no one was hurt.
For
the airbag deployment, rapid deceleration followed by any kind of impact is the trigger? If the OP had braked equally hard but not hit the dog, the airbags wouldn't deploy, right ?
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Old 27th May 2013, 10:15   #8
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Default re: Airbags deployed after hitting a dog. Understanding why?

Thanks for sharing your experience. I am interested to know:
* Did your face hit the airbag?
* If yes, did it hurt?
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Old 27th May 2013, 10:35   #9
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Default re: Airbags deployed after hitting a dog. Understanding why?

Quote:
Originally Posted by vikram_d View Post
One important point to note is that airbag deployment does not depend on impact intensity alone. It also depends on rate of deceleration. The airbag controller does not know that you hit a dog. It just sensed high rate of deceleration and then an impact and it did what it was programmed to do. Deploy air bags.
Quote:
Originally Posted by 999 View Post
I too think that you tried too hard to save the dog and stood on the brake. This should have triggered the sequence. The same braking force and impact can also happen if you narrowly missed being crushed by a trailor because you managed to stop in time, but hit it slightly (The airbag system does not have eyes !!) with can equate to a 30Kg dog as you mentioned.It detected just frontal impact and no roll over so the side curtain airbags did not deploy.
I don't disagree with you but not entirely convinced either. I read through the wiki notes and also as per my understanding airbags deploy in a situation where rate of de-acceleration is extremely high. When I say high, think of a car that is travelling at 40-50kmph and hits a wall or a tree or a pole. At that point the car virtually goes from that speed and stand still within few cms and that triggers air bag deployment due to very high frontal G force that is created. Now in my case even if i braked really hard but with a car with ABS its normal to have that kind of de-acceleration and hitting a dog which is say 1/40th the weight of the car is not going to cause any significant change in momentum of the car to trigger air bag event. Impact is there but its the severity or rate of change of de-acceleration that decides deployment or no deployment.

Quote:
Originally Posted by Alter_Ego View Post
OT, just wanted to know what happened to the dog.Since the damage to the Mazda's bumper was negligible, does that mean that the dog took the major impact ?
Unfortunately ofcourse dog took maximum hit and eventually was run over by more traffic. May the dog RIP.

Quote:
Originally Posted by lancer_rit View Post
Good to hear no one was hurt.
For
the airbag deployment, rapid deceleration followed by any kind of impact is the trigger? If the OP had braked equally hard but not hit the dog, the airbags wouldn't deploy, right ?
Well ideally if I didnt hit the dog there would be no airbags as then it would be a normal braking scenario. The point we are trying to understand is what defines an "impact" even. Its not just any impact, there is specific measure to the severity that causes the deployment.

Quote:
Originally Posted by EagleEye View Post
Thanks for sharing your experience. I am interested to know:
* Did your face hit the airbag?
* If yes, did it hurt?
No the air bag only hit my chest. Primarily because the seat belts had pre-tensioners which pulled me back into the seat pretty darn tight. Without the pre-tensioners its likely that air bag can hit the face. Though i dont think it would hurt. I did feel a thud to my chest but didnt hurt much. Btw the air inside the airbag is really hot and that can cause some burns if it leaks on the skin. The steering area where the air bag deploys was extremely hot and I coudn't touch it for 10 mins or so

Last edited by supertinu : 27th May 2013 at 10:40.
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Old 27th May 2013, 10:50   #10
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Default re: Airbags deployed after hitting a dog. Understanding why?

Thanks for sharing.

Good to know you are safe. Never experienced airbag and praying not to experience in future as well .

Normal sized Dog itself is good enough to cause serious damage to a car. Just recollect my friend's Corsa got serious damage after hitting a dog in Mysore - Bangalore highway including damaged AC & Radiator, bumpers and grill.

As suggested by all, though the impact of hitting the dog is not so high in your case, heavy braking would have triggered the seat belt tensions and airbag.
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Old 27th May 2013, 11:23   #11
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Default re: Airbags deployed after hitting a dog. Understanding why?

Quote:
Originally Posted by supertinu View Post
This makes me feel a bit concerned cause I have a Figo with airbags and hitting a dog on Indian highways is not unlikely
Impressed the way Avis dealt with the issue. Any paper work delay from their end would have caused you to miss the flight.

Hitting a dog on Indian Highways should be last on your worries list. A tractor carrying marriage party travelling on wrong side, broke down truck on right lane without hazard lights in night, moped on wrong side, cows (remember a forum member having met with an accident), kids darting across ( another forum member has got Innova crashed trying to avoid the kid). The list is endless. I guess the golden rule in India is to keep the speed limited to sub 90 KMPH range always no matter how inviting the highway looks.
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Old 27th May 2013, 12:01   #12
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Default re: Airbags deployed after hitting a dog. Understanding why?

Very interesting case!!

The airbag sensing system deploys based on Acceleration (Force) and The rate of deceleration (delta velocity). this is purely newtons second law of motion. When the force is sufficiently high and at the same time, the deceleration is also high then the bag / belt deploys.

The airbag sensing system has two types of sensors -
1) Internal sensors (Mounted inside the ECU, The ECU is located between the handbrake & fire wall)
2) External sensors - Mounted on the front end module for frontal crashes & mounted on the pillars for side crashes

In this case particularly, it is unfortunate that this situation should not have deployed the bag. This case is very similar "Deer Impact case of US" where the bags are not expected to deploy. This is an inadvertent deployment of the bag.

I can say two things looking at the pictures -

1) The frontal sensors are poorly calibrated, making them more sensitive to such events
2) May be mazda has not considered such events as "Deer Impacts" dont happen in middle east.
3) the passenger bag is deployed (was there a passenger?) i am assuming no. This should not have happened at least.
4) There is no noticeable deformation in the front of the car

But i am glad, you have been able to write this post and doing very well.
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Old 27th May 2013, 12:05   #13
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Default re: Airbags deployed after hitting a dog. Understanding why?

Quote:
Originally Posted by mpksuhas View Post
Impressed the way Avis dealt with the issue. Any paper work delay from their end would have caused you to miss the flight.

Hitting a dog on Indian Highways should be last on your worries list. A tractor carrying marriage party travelling on wrong side, broke down truck on right lane without hazard lights in night, moped on wrong side, cows (remember a forum member having met with an accident), kids darting across ( another forum member has got Innova crashed trying to avoid the kid). The list is endless. I guess the golden rule in India is to keep the speed limited to sub 90 KMPH range always no matter how inviting the highway looks.
You are right about dogs not being the biggest worry on our roads. I hope I never experience airbag deployment again but my main point was that I dont want to spend 1lac+ in repairs just cause I hit a dog on the road and air bags deployed.
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Old 27th May 2013, 12:48   #14
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Default Re: Airbags deployed after hitting a dog. Understanding why?

Quote:
Originally Posted by groom View Post
3) the passenger bag is deployed (was there a passenger?) i am assuming no. This should not have happened at least.
Well this deployment actually depends on the presence of a PPD (Passenger Presence Detection) and a OCS (Occupant Classification System) in the car.
Though I do think that they would have been present. If there was no passenger, then definitely it is a unwanted deployment. Or, it could also be that the OP has put some luggage in the passenger seat, but then again the seat belt would not have been buckled, which should ideally lead to no deployment!

Regarding the deployment of airbags in general, there is a plausibility check between the inputs from the external and internal sensors and the decision is taken accordingly. I would be really interested to study the EDR (event data recorder) of the car and come to conclusion. I do think that AVIS would be required to do this anyways. Can the results be shared by the OP by seeking them?
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Old 27th May 2013, 13:50   #15
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Default Re: Airbags deployed after hitting a dog. Understanding why?

Quote:
Originally Posted by groom View Post
Very interesting case!!

1) The frontal sensors are poorly calibrated, making them more sensitive to such events
2) May be mazda has not considered such events as "Deer Impacts" dont happen in middle east.
3) the passenger bag is deployed (was there a passenger?) i am assuming no. This should not have happened at least.
4) There is no noticeable deformation in the front of the car

But i am glad, you have been able to write this post and doing very well.
Dont know about Deer Impacts but the guy at Avis told me of cases where Camels walked over onto the highway.

Quote:
Originally Posted by MotoNanu View Post
Well this deployment actually depends on the presence of a PPD (Passenger Presence Detection) and a OCS (Occupant Classification System) in the car.
Though I do think that they would have been present. If there was no passenger, then definitely it is a unwanted deployment. Or, it could also be that the OP has put some luggage in the passenger seat, but then again the seat belt would not have been buckled, which should ideally lead to no deployment!

Regarding the deployment of airbags in general, there is a plausibility check between the inputs from the external and internal sensors and the decision is taken accordingly. I would be really interested to study the EDR (event data recorder) of the car and come to conclusion. I do think that AVIS would be required to do this anyways. Can the results be shared by the OP by seeking them?
Yes it seems like the car didn't have any form of PPD though its a bit surprising since it had all other features like pre-tensioners etc. I can understand my figo not having this feature. Also the passenger seat only had few papers, a phone and a wallet on it and I am sure that wouldn't classify as enough weight to trigger false alarm in the system.
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