What is the value of an ABW (Advanced Brake Warning) system?

Dear Car Talk

Dear Car Talk | Jun 01, 2000

Dear Tom and Ray:

What can you tell me about the ABW (Advanced Brake Warning) system? How come there isn't a law requiring its installation on all new cars (like the third, high-mounted brake light)? In Israel, where I live, dealers commonly install the system on new cars as an added safety feature. It isn't very expensive, and I'm wondering why safety organizations and insurance companies aren't demanding that it be installed at the time of manufacture? -- A.J.

TOM: I assume you're talking about one of the systems that displays the intensity with which one is stepping on the brakes, right? There are several such systems that have been invented.

RAY: One of them makes the brake lights flash faster as the pedal is applied with more pressure. Another makes the brake lights grow brighter as the pedal nears the floor. And all of them are designed to let the driver behind you know whether you're just tapping the brakes as a cautionary move, or slamming them on full to stop at a doughnut shop that's having a close out.

TOM: My brother happens to think this is a great idea. In fact, he's convinced that he invented the idea. Then again, if you put an ice cube in his hand, five minutes later he'd be convinced he invented water.

RAY: The National Highway Traffic Safety Administration (NHTSA) HAS looked at these systems extensively. But they found no convincing evidence that ABW would prevent accidents. And NHTSA refuses to make something mandatory for manufacturers unless there is clear evidence that it will have a real effect on accidents and injuries.

TOM: You would think, intuitively, that knowing how hard someone in front of you is applying the brakes could only help you. But what NHTSA found was that people didn't have time to process the extra information. The brake lights themselves are sort of a warning light that's supposed to get your attention and get you to put your foot on YOUR brake pedal immediately. The tests showed that there was just no time -- in real-world situations -- for people to process and make use of the flashing frequency or intensity of light before emergency action was required.

RAY: They also found that the flashing could be confusing to drivers, and that the variation in brightness of the lights was difficult to read quickly.

TOM: Their conclusion was that this sort of advanced brake warning system is not worth the cost and wouldn't really aid in preventing accidents.

RAY: They came to the opposite conclusion, by the way, about the high-mounted third brake light. That did seem to prevent accidents and has been mandatory for some years now.

TOM: Perhaps over time, data from another country, like Israel, might provide some convincing evidence. But until NHTSA sees that, you won't be seeing any such advance brake warning systems here in the U.S. of A.

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