Brake Override Systems Explained

At a time when the automotive industry is hit by one of the largest recalls ever, automakers are trying to develop new and safer technologies that would be able to prevent all kind of problems that might occur while driving. And taking into account the very advanced hardware and software components a car is equipped with nowadays, such a task could prove to be a bit harder than initially expected.

It happened to Toyota and, although the solution was as obvious as it could get, integrating it into its models could actually led to a different kind of problems.

We're talking here about the brake override system, Toyota's simple solution to the stuck accelerator pedal that affects millions of cars but, more importantly, killed drivers and passengers around the world.

In short terms, a stuck accelerator pedal basically means that the driver loses control over the throttle and, depending on a number of factors, over the whole vehicle. If the car is equipped with a manual transmission, the solution is fairly simple and the driver can get out of a life-threatening situation in a second: just press the clutch and switch the gear stick into neutral. Even if the accelerator is stuck, the car should not be able to speed up, so the vehicle should come to a halt after all.

But what happens if the vehicle features an automatic gearbox, as it's the case of most cars sold in the US? Well, things are a little bit more complicated and, although there are some steps to be followed, let's concentrate on the brake override system.

Without going too much into detail, Toyota have experienced this on their own. Although the Japanese manufacturer claims this wasn't the case, rumors were suggesting that a short-circuit disabled the braking system entirely, while the car was continuously accelerating. Recordings of 911 calls made by Toyota or Lexus drivers who got the accelerator pedal stuck claimed that the brakes were indeed nonfunctional.

After further investigation, Toyota has come to a simple, smart, less expensive and easy to implement solution: the installation of brake override systems in all new cars, plus in those affected by the glitch.

The way the brake override system works is not so complicated as some may be tempted to believe. All in all, such a technology is designed to make the brake efficient even if the accelerator pedal is stuck and thus assist the driver into bringing the car to a halt.

The brake override system collects information from speed sensors, accelerator pedal position sensors and brake light switch circuitry. In case both pedals are pressed, it brings the engine revs down and reduces the speed as if the throttle is not blocked. Still, once the vehicle is completely stopped, you're recommended to put the gear stick in neutral, just to be sure that the car doesn't start re-accelerating.

The system only works at speeds greater than five miles per hour (8 km/h) and when the brakes are firmly applied for longer than one-half second (quote from Toyota's official information, so details might be slightly different depending on the manufacturer). In Toyota's very own version, the brake override system does not work if the brake pedal is depressed before the throttle, thus allowing the car to accelerate without rolling backwards on hill or in similar conditions.

In other cases however, the brake override system was adopted a long time ago and continues to be improved every once in a while. BMW for instance rolled out the latest version of the system in 2005, with the whole assembly relying exclusively on software configuration. To give you an idea on how costly such a system is, a mechanical system is believed to go around 50 bucks while a software setup could have a price of several hundreds dollars.

As you can see, especially after the many accident caused by unintended acceleration on Toyota vehicles, such a technology is extremely useful and, in some cases, can even save the life of both the driver and the passengers. Some people involved in the automotive industry think that brake override systems should be made mandatory on new cars, just like ABS and airbags, but a decision on this is yet to be made.