Airbags – Pillow or Projectile?

Q: I have a car with ten air bags. If I get in a crash I’m going to be floating in a balloon-filled cabin. With that many airbags, is the seat belt still necessary? I realize it’s the law, but from a safety perspective how much does it help anymore?

A: Not only are airbags an effective safety feature; they also function as a prompt for jokes. Like these: New cars come with up to a dozen airbags, and that doesn’t count your passengers. New cars have so many airbags that they’re beginning to rival a political convention. Airbags – inspired by a road trip with your in-laws. I didn’t promise they’d be good jokes.

You might think that with all those balloons inflating almost instantly in a crash, a seat belt isn’t as important as it once was. And if you did think that, you’d be mistaken.

If you look closely at your steering wheel and the other airbag locations in your car, you’ll probably find the letters “SRS”. That stands for “Supplemental Restraint System.” Airbags are designed to supplement seat belts, so there’s a design assumption; people in the car are wearing seat belts. That’s a reasonable expectation; in Washington, for example, 93 percent of us wear a seat belt.

Seat belt effectiveness is undebatable. I mean, I guess you could debate it, but every data source I’ve come across says you’d be wrong. Wearing your seat belt drops your risk of a fatal injury in a crash by 45 percent. 

By some estimates, seat belts combined with airbags push that over 60 percent. Airbags alone, though, are not so impressive. According to the National Highway Traffic Safety Administration, in 2017 seat belts saved 14,955 lives, while airbags saved 2790 lives. Yes, airbags save lives, but they’re no seat belt. And on their own, they can inflict harm too. When you wear a seat belt in a crash, your airbag helps to further decrease your odds of injury. That nearly instant inflation isn’t so great though if you’re not wearing a seat belt.

Consider what happens in a head-on crash. Newton’s First Law of Motion states that an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force. When a car stops upon impact, the driver of that car continues in the same direction and speed until they’re stopped, by the seat belt and airbags when used and so equipped, or by the steering wheel and windshield when not used.

The seat belt restrains your torso, but at the top of your torso is a ten-pound ball with some stuff in it that you depend on for survival. That ball keeps moving forward until stopped by your neck. The airbag fills in that space, supporting your head and spreading out the overall impact to your body.

Without the seat belt though, in a crash you’ll be rapidly moving toward a balloon that’s exploding at 100 to 200 mph. When it’s fully deployed it’s a cushion; but at first it’s a rocket. Get too close and you have the potential for serious injuries from the airbag. The seat belt keeps you in position to get the safety benefits of the airbag and avoid the initial giant punch from it.

For all the lives saved by airbags, there have been some fatalities (partly because early airbag designs were too powerful), but in over 80 percent of those deaths the people were not wearing a seat belt or improperly restrained. Airbags work, but only when paired with your seat belt.