What you Need to Know About Anti-Lock Braking Systems

A Canadian Direct Insurance Claim:

A Canadian Direct customer was proceeding south on Victoria Drive at a T-intersection. A pedestrian stepped off a curb to cross the street, despite there not being a crosswalk here. The first two drivers in line slammed on their brakes and stopped. The customer, who was following these two cars, "slammed on his brakes and skidded into the back of them." At the time, the roads were dry, and the customer was driving a vehicle equipped with an Anti-Lock Braking System (ABS). Fortunately, there were no injuries, although there was damage to front bumper, grill, and hood of the customer's vehicle.

Could This Accident Have Been Avoided?

In reading over hundreds of CDI claims, this is not the first one that I had to question a bit. After all, the customer claims to have skidded while driving a vehicle equipped with an Anti-lock Braking System (ABS). It is simply not possible for a vehicle with ABS to lock up the brakes and skid.

My guess is that he was simply following too close to the vehicle in front, not allowing enough room to stop, no matter what type of braking system his vehicle had. Or, he miss-used the Anti-lock Braking System.

Without a doubt, Anti-lock Braking Systems (ABS) are the most significant safety development since the seatbelt. If you currently drive a vehicle without ABS, and you learn anything from this article, I hope it's that the next vehicle you purchase must have ABS. It's that valuable. Once you have ABS, though, it's important to fully understand how to effectively use the system to your advantage, and perhaps even more importantly, what its limitations are.

Unfortunately, many drivers who now drive a vehicle with ABS do not know how to fully use it. And then there are some who believe ABS can perform miracles. Remember that when a wheel locks-up (stops turning) and skids you have no steering control over that wheel. In other words, if you lock-up the front wheels by braking too hard, it doesn't matter what you do with the steering wheel, the car is not going to go where you want. Plus, your stopping distance is going to increase. A tire that is skidding will not slow you down as quickly as one that is turning just at that limit before it locks-up (that's called threshold braking).

So, how does ABS work?

Basically, there are sensors at each of the four wheels (or in the case of the less sophisticated three-channel system, one on each of the fronts and only one for the pair of rears). These sensors watch the rotation of the wheels. When any one of the wheels stops rotating due to too much brake application, the sensors tell the car's computer, which then releases some of the brake line pressure that you've applied - allowing the wheel to turn again. Then, just as fast as it released the pressure, the computer allows the pressure to be applied again - which stops the rotation of the wheel again. Then it releases it again. And so on. With most ABS, this releasing and re-application - or pulsing - of the brake pressure happens 20 or more times per second.

Practically speaking, this keeps the wheel just at the limit - the threshold - before locking up and skidding. ABS prevents you from ever locking up the brakes and skidding - no matter how hard you apply the brakes. Obviously, this is going to mean much more steering control.

With ABS, all you have to do in an emergency is quickly squeeze the brake pedal as hard as you can and hold it there. And when I say hard, I mean HARD. Let the system do the finesse work for you. This may not be as easy as it sounds. After years of being told (and practising) not to press too hard on the brake pedal, this may not feel very natural.

So, practice squeezing hard. Make sure you know what it's like to use the ABS. Get use to the feel of the pedal. You are going to feel the pulsing of the system in the pedal and hear some different noises. At first, it's very un-nerving. It feels as though you're hurting the car.

Many drivers, in fact, upon feeling the pulsing and hearing the noise from the ABS, ease off the brakes - even in an emergency! That may be what the driver in our claim did. It is a situation where the car has the capabilities of avoiding the possible crash, and yet the driver - due to unfamiliarity with these capabilities - doesn't use them fully. The result is often an unnecessary crash.

All this makes ABS sound as though it can perform miracles. Well, not quite. It does have limitations. Let's take a look at some of them.

Three points should be obvious, but don't appear to when looking at the type of crashes some drivers have with ABS-equipped vehicles. Contrary to popular belief, ABS:

• does not allow you to drive faster;
• does not allow you to brake later; and
• does not allow you to corner faster.

Too many drivers think that once you have ABS, you can do all of the above. When many of the police departments in North America first got cars equipped with ABS, the officers began having more crashes. There were even some who screamed about getting rid of the ABS. They claimed ABS was dangerous.

It wasn't the ABS causing the problem. It was a simply a case of not being properly trained. They were told ABS could perform miracles. They would then drive faster, brake harder, later and more often, and try taking corners faster than ever before. Usually, this would result in some overheating of the brakes (which any vehicle will experience if abused by overdriving) and crashes.

You have to understand that ABS does not raise the traction limits of your vehicle. It only helps you stay within the limits. Period. So, don't get caught up in believing that ABS will allow you to drive any faster, brake later or go around a corner any faster - or allow you to safely follow any closer.

Finally, there is a great difference between ABS and Rear Anti-lock Brakes. ABS is on all four wheels. Rear Anti-lock Brakes, as the name suggests, are only on the rear wheels. This system is often used on pick-up trucks and vans, and is a less-expensive compromise. It is used because the weight load on the rear of a truck or van can vary so much. The brakes needed to handle a heavily loaded vehicle are too effective for when it is lightly loaded. Therefore, the rear brakes are much more susceptible to locking-up.

I would never buy a vehicle with a Rear Anti-lock Brake system. Being able to steer while braking is one of the most important features of ABS. With Rear Anti-lock Brakes, this is not always possible, as the front wheels can still lock up. Plus, many people have been sold the vehicle believing they have full ABS. Imagine their dismay the first time they used ABS in an emergency.

So, if buying a truck or van, be sure you know if you're getting ABS or just Rear Anti-lock Brakes (if the salesperson does not know the difference, I strongly suggest you go elsewhere). If necessary, spend the extra money and get ABS. Having mentioned all these limitations, I still believe ABS is the most important safety feature you can get on a new vehicle. I would not buy one today without it. All you have to remember is that you, the driver, still have control over any and all of these limitations. A vehicle's braking or cornering limit is determined by the tire's traction limit - not by the type of braking system. ABS does not allow you to drive faster, or brake later. It just helps eliminate the results of driver error - a locked-up, skidding vehicle. So, learn to take advantage of the fantastic technology of ABS, but respect your vehicle's limitations.