How Automatic Braking Systems Work

Safety First

Subaru's EyeSight system uses two black and white cameras that work like your eyes to triangulate the speed and distance of the vehicle in front of you.
Subaru's EyeSight system uses two black and white cameras that work like your eyes to triangulate the speed and distance of the vehicle in front of you.

Both Subaru and Volvo -- and really any manufacturer you talk to, as long as it's not Audi with its self-driving car -- make it clear that they are not trying to take driving away from the driver. "If any system begins activation but the driver decides to steer away, you will not be in a fight with the vehicle," Kopstein said. "The car will release the brakes so you can maneuver out of the situation." Sullivan put it even more plainly: "We want you to drive the car."

So, if no one is trying to take away the driver's responsibility, why bother to have the car do the braking for you at all? Why not just beep or blink or, in the case of Cadillac, vibrate the seat to let you know you need to pay attention and drive the dang car?

Research says that a third of all reported collisions happen when a front bumper meets a rear bumper. And in half of those accidents, the driver of the rear car doesn't brake at all. So, apparently, we could use a little help in the braking department.

The IIHS determined that cars with automatic braking systems had between 14 and 27 percent fewer insurance claims for damage to cars, depending on the system. And that was for 2010 cars, which is practically the dark ages for these systems.

Besides, automatic braking doesn't operate alone. It's part of more comprehensive systems that include throttle management, lane departure warnings, adaptive cruise control and other safety systems. And the technology is only getting better, with better cameras and sensors. As the technology moves forward (EyeSight and City Safety are both already on their third generation), it'll get cheaper, and as it gets cheaper, it'll be in more cars, which benefits everyone. Even the woman in the muumuu driving the Humvee.

Author's Note: How Automatic Braking Systems Work

When I set out to write this article, I drew up a little plan for myself: Who to talk to, what to include and what the final version would look like. It was a terrible plan.

That's because these systems are far more sophisticated than I expected. Like Adam Kopstein at Volvo said, "Making the car stop is easy." That's what I figured. What I didn't count on was that next part of his quote: "The trick is making sure it only does it when it's supposed to." The variety of sensors, cameras, recognition profiles, warnings and brake applications for this one little part of a safety system made for a very complicated explanation.

So I had to revisit my plan. And by "revisit," I mean toss-out completely and let my conversations with the experts guide the story. There's so much more information that I wish I could have fit into this article! Like how Volvo tested its cameras in European taxis, and the resulting images nearly gave the researchers heart attacks. And how EyeSight will tell you if the car in front of you has pulled away from the red light while you continue to sit there playing Angry Birds and holding up traffic.

Related Articles


  • Edelstein, Stephen. "Cadillac's automatic braking system acts like a 'virtual bumper.'" Digital Trends. Sept. 18, 2012. (Jan. 28, 2013)
  • Insurance Institute for Highway Safety. "Crash avoidance technologies." July 2012. (Jan. 31, 2013)
  • Kopstein, Adam. Volvo safety and compliance manager. Personal interview conducted on Jan. 30, 2013.
  • O'Donnell, Jayne. "Automatic braking in cars helps cut down on crashes." USA Today. July 19, 2011. (Jan. 28, 2013)
  • Sullivan, David. Subaru EyeSight expert. Personal interview conducted on Jan. 29, 2013.
  • Subaru of America. "2013 Subaru Legacy Debuts New Powertrain, EyeSight Driver-Assist System and Revised Styling." Aug. 12, 2012. (Jan. 28, 2013)
  • Volvo Car Group. "Collision Warning with Auto Brake helps prevent rear-end collisions." Jan. 11, 2008. (Jan. 31, 2013)