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"How fast" do I have to go to get an airbag to deploy?

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"How fast" do I have to go to get an airbag to deploy?

Post by Rusty Haight » Mon Apr 09, 2012 2:01 pm

See also related topic: "Delta-V of "8/10/12" and deployment logic"

Recently, I've had more requests than "normal" along the lines of "how fast do I have to be going to get an airbag to deploy," or "what impact speed is required to get an airbag to deploy?" This prompted some light research into what's being said on the internet that I thought Forum members might find interesting.

From "Yahoo! Answers:
...I believe I was traveling somewhere around 25mph when the accident occurred and my airbags went off. The front of my car is pretty smashed in, and the car is probably totaled, etc. My paranoid Mother claims you have to be going much faster than 25-mph to set off your airbags, but I'm 98% sure that is wrong....

Some of the answers there weren't too terribly bad...

From "how fast do you have to go for airbags to deploy"
...Generally speaking over 25MPH. The impact must be frontal and not side. Thats 25mph as if you hit a wall, non moving obsticle. If you hit a car from behind and it moves forward then the impact must be much greater to fire the bags. Also hitting a car head on when both vehicles are moving at say 12MPH will set them off. So any combined frontal force over 25MPH will usually do it.

and a couple personal favorites from the RX8 Club.vom forum "what does it take to set off a airbag":
...This is only a guess on my part but if you locked the wheels during your skid the car could have been sliding more that 40 MPH but the computer thought is wasn’t moving at all. Speed of impact is the main thing that controls the bags. Wheels not moving hitting the back of a truck going forward = not enough the set off the bags?? Again just thinking out loud ...

...Correct me if I'm wrong...air bags deploy when the sensor in the panels and bumpers are activated (hit by the other car)...

And then there are the significantly better technical references like this from topic "Airbag Deployment with an Aftermarket Bumper". There's actually some good information sprinkled into that Forum thread.

There's still a lot of misinformation out there about "when does an airbag deploy" and this might be a good place to collect some of the really odd (and some of the really good) references.
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Collision Safety Institute

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Re: "How fast" do I have to go to get an airbag to deploy?

Post by seanhaight » Mon Apr 09, 2012 3:33 pm

For what it's worth, NHTSA states:

Air bags are typically designed to deploy in frontal and near-frontal collisions, which are comparable to hitting a solid barrier at approximately 8 to 14 miles per hour (mph).

They also go on to say:

Roughly speaking, a 14 mph barrier collision is equivalent to striking a parked car of similar size across the full front of each vehicle at about 28 mph. This is because the parked car absorbs some of the energy of the crash, and is pushed by the striking vehicle. Unlike crash tests into barriers, real-world crashes typically occur at angles, and the crash forces usually are not evenly distributed across the front of the vehicle. Consequently, the relative speed between a striking and struck vehicle required to deploy the air bag in a real-world crash can be much higher than an equivalent barrier crash.

Because air bag sensors measure deceleration, vehicle speed and damage are not good indicators of whether or not an air bag should have deployed. Occasionally, air bags can deploy due to the vehicleÕs undercarriage violently striking a low object protruding above the roadway surface. Despite the lack of visible front-end damage, high deceleration forces may occur in this type of crash, resulting in the deployment of the air bag.

Most air bags are designed to automatically deploy in the event of a vehicle fire when temperatures reach 300 to 400 degrees Fahrenheit. This safety feature helps to ensure that such temperatures do not cause an explosion of the inflator unit within the air bag module.

Front air bags are not designed to deploy in side impact, rear impact or rollover crashes. Since air bags deploy only once and deflate quickly after the initial impact, they will not be beneficial during a subsequent collision. Safety belts help reduce the risk of injury in many types of crashes. They help to properly position occupants to maximize the air bags benefits and they help restrain occupants during the initial and any following collisions. So, it is extremely important that safety belts always be worn, even in air bag-equipped vehicles. ... page3.html
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Re: "How fast" do I have to go to get an airbag to deploy?

Post by carcrash123 » Fri Mar 14, 2014 4:17 pm

I got in a car accident today, i assumed i was going 35 because i was in a 25 and by the damage done. I hit a 6-foot rock that was pretty heavy, that then set off my airbags, then i hit a mailbox and ran it completely over, then after that i hit a telephone pole and dented that. i would have had no injuries if the airbag didn't open but it did and when it did it cut my arm in 3 spots, and cut my leg in one. The whole point is that it doesn't take a lot of speed to deploy an airbag, and in my case, the airbag was useless.

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Re: "How fast" do I have to go to get an airbag to deploy?

Post by sd3225 » Tue Mar 25, 2014 8:18 pm

you will know... when it happens !!

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