Does anyone know why my airbags didn't work when I was hit head-on by another car traveling at 30-35 mph? I have a 2003 E500 and was at a full stop at a traffic light when the other car slammed into me. I had my seat belt on as well. The Mercedes dealer said that the airbags didn't deploy because I was not moving. That doesn't make much sense to me because that thinking means that I could have been hit head-on by a truck going 80 mph and the airbags would still not have deployed. Thanks.

 

I always thought the sensors measured what the force of impact was and then made the determination to deploy or not.

I'd take pictures, and keep records. You maybe able to lemon the car. Dealers will tell you anything to leave them alone.

 

Did you or anyone else in the car recieve any bad injurys? If not then that is why the airbags didn't deploy, they will only deploy if the collision is severe enought to cause you nasty injurys. Airbags themselves injure people so they are now only triggered to go off when REALLY needed and not when you clip a pebble.

 

Thanks for the replies. Do you know the criteria for deployment of the airbags? I was at a full stop and after impact with the other car (a Honda Civic) my car was driven back fifteen feet. I would think that impact would be sufficient for my airbags to deploy.

 

I don't know the criteria for airbag deployment, but if your car was at a full stop when it was hit head on, then your body was moving backwards away from the airbag/steering wheel. Maybe that's why the airbags did not deploy (ok, your body would actually be sitting still while the steering wheel moves towards you initially during the impact, but depending on the severity of the impact, I would guess that you moved backwards with the car).

 

Were you hurt at all? If not then the car did its job.

 

Need pics!!!! I have seen some crashes that pinned the driver and no bags deployed because the bumper did not take any of impact. I have also seen low speed crashes, less than 10 mph, with no visable damage to the bumper deploy the bags.

Cheers,
Steve
Rescue 14 "A" shift

 

I agree, for those that like to download Top Gear and 5th Gear episodes and saw the fixed head on collision between the two Renault Espaces know about this, if the airbags didn't deploy the car decided to save you $$,$$$ because with the passive systems it was enough.

 

The airbag was to help to stop your body from moving forward when your car get hit, this help to lesser internal damage.

When your car is moving, and hit something, by momentum, your body still move, and this is why airbag deploy to save you.

When your car is at stop, even if something hit it, there's no moving momentum on your body, and that's why airbag did not deploy.

 

Mercedes airbags do not employ an impact sensor like most other cars. They measure the g force of the impact with an decelerometer that is (I think) between the passenger seats. Thus an impact in and of itself will not deploy the airbags. Only a sufficient DEceleration will cause this. In an ACceleration such as getting hit while stopped your body is supported by the seat and airbags would be useless.

 

The probable reason that your airbags did not trigger is that your car moved fifteen feet backwards. This allowed the impact force to be dissipated over a longer period of time. It's all to do with kinetic energy.

Let's say a car weighing 1500 kg, is travelling at 120 km/h (34 m/s). The kinetic energy is 1/2 * 1500 * 34 squared, which is 867,000 Newtons.

Which is going to be more devastating, a crash that dissipates 867,000 Newtons over 15 meters or a crash that dissipates that force over just 1 metre?

Or, imagine catching a baseball. What will hurt your hand more, catching a well hit ball and not moving your hand or catching the ball and moving your hand backwards to cushion the impact?

Imagine the much larger surge impact force that would have occured if your car did not move backwards at all, then I am sure that the airbags would have deployed.

That's why I would rather roll my rally car (full roll cage and harnesses) for 30 or 40 metres than hit a tree head on. The same amount of force is dissipated over a larger amount of time.

 

80% of all makes air bag sensors deploy by means of G-forces that the sensor is attached to during impact. That includes Mercedes Benz as well. (25 years in the autobody/refinish industry)