In order to help you stop todays vehicles often include electronic brake management systems. Terms such as ABS (anti-lock braking system) and EBS (electronic braking system) probably ring a bell. They prevent locking-up the wheels under heavy braking.
When such a system detects that a wheel is about to lock-up it quickly reduces braking pressure and pulsates the braking force up to 60 times a second.
The major advantage of these systems is that steering movements remain possible under heavy braking. However ABS and systems alike do not always guarantee a shorter stopping distance. In fact on slippery road surfaces it can actually increase the stopping distance if you're braking beyond the point of maximum grip.
In situations such as rain or snow there is not a lot of traction available left for braking. Heavy application of the brakes on such surfaces can produce somewhat strange results if the vehicle is equipped with ABS.
Braking hard in a car without ABS on low traction surfaces can easily result in locking-up the tires if you're not an experienced driver. If the car is equipped with ABS the system will constantly want to interfere whenever you're stepping on the brakes too hard, braking beyond the point of maximum grip. Now because the ABS system constantly interferes with your braking this will only increase the stopping distance.
Compared however to locking-up the tires and skidding your way to a halt in a non-ABS car, this system does indeed help shortening the stopping distance.
LOCKING-UP THE TIRES DOESN'T HELP AT ALL
Youve probably also heard about pumping the brakes. It sort of resembles an ABS-system, quickly going on and off the brakes. Also known as candence braking, this is not really a racing technique; its more a braking technique for in case of emergency.
This was especially effective back in the old days when the brakes werent really up for the job. It has only one major advantage.
Braking and steering at the same time
The maximum grip the tires deliver can is only so much. You can choose how to use this grip for either steering, accelerating or braking.
If you brake hard there's little room left for steering. If you then go beyond the point of maximum grip the tires will lock-up and slide uncontrollably.
If you are steering you can brake a lot less compared to when braking in a straight line. And of course, vice-versa, if you brake hard, you will have to sacrifice some of your steering ability so you don't lock-up the tires.
So if you ever have to make an emergency stop and you need to steer while braking, remember that pumping the brakes can be very effective. This technique is only being used in emergency situations on cars that don't have ABS. And nowadays most cars have ABS. For racing this is not very effective a very effective technique, in racing a braking technique called threshold braking is used.