[MUSIC] Hey folks. Cooley here with another one of your emails about high tech cars and modern driving. This one comes in from Gerald Tee in New York who says I love watching crash test videos and noticed recently some cars will deploy both side curtain airbags in every crash While other cars will deploy only one. He says, I presume it would be safer to be in a car where both deploy all the time no matter the type of crash. Why don't all cars do this? Well, a lot goes on with the airbags Gerald. It's a very complex decision to fire one of those things or not. Let's look at the basics here of what goes on in a crash. A collision is not just a collision, it's typically four collisions. First of all, you've got the one between your car and the other car. Then you've got the one that happens with you versus The inside of the car when you're bouncing off the interior, which is a lot of hard parts covered in soft parts. Then, once you hit them, there's the collision inside of you. Your organs hitting the inside of your body, organs against rib cage, brain against skull. And finally in many crashes there's also the loose flying object collision Your kid's laptop, flying up from the second row, hitting you right in the head. So all of these are what we're trying to deal with. Airbags can help with some. Not with the flying laptop, of course. Now why airbags don't all fire all the time is for two major reasons. Number one, you're trying to actually control the injuries they cause. These are not completely inert devices. Any EMT will tell you about the kind of injuries they see from airbags. Things like blackened eyes, first degree burns on forearms, even some break Fingers and wrist, so you don't fire these things trivially just to do so. Secondly, hopefully, carmakers are trying to control the cost of SRS airbag replacement. They're about $1000 each to replace after a collision if you've been in a minor to moderate collision that could be a huge part of your body shop repair bill. The decision was made back around the year 2000 to have a much more nuanced airbag system with a variety of sensors reporting into this guy. This is a box, often called a black box, but it's an ACM. It's an airbag control module. It's a computer than has a certain amount of data, a small snapshot, that it's using to compare what's just happened with the car to what's happening now and make a decision if it's turning into a crash scenario. The airbag has to inflate in a way that you hit it, right at the time of peak inflation which is super quick, it's about a 20 milliseconds event inside a 70 to a 150 milliseconds crash. All of these happens literally, the blink of an eye or less The deceleration rate is the key here. Not just the raw speed of the vehicle, but how fast is it scrubbing off speed. You know what they say, speed doesn't kill. It's the stopping that'll get you. And that's what the sensors around the car are looking for and reporting into the ACM. The ACM is also triangulating those reports from sensors to figure out what direction the deceleration is happening. It's not just a world or rear-end collisions. A lot of cars have lateral, partial frontal, or roll over, and that's gotta be determined as to which airbags the fire and which ones to lead in [UNKNOWN]. And the car structure has to be programmed into the ACM's logic. Different cars collapse in different ways when they hit the same object at the same speed. And you gotta make sure that that's a factory built into the algorithm, so we still end up with the same result. What do I have to do with the airbags to prevent you bouncing off the inside of the car? And finally, the distance and location of each airbag has to be factored in. You're much closer to the one on the side, protecting you from the pillar than a passenger is from the one in front of them protecting them from the dash and windshield. So you'll get to the hard part faster, and the air bag has to deploy harder to get to you faster to prevent that. I think with all this mind you can see why we have a need for a new bumper sticker out there. [MUSIC]