Give Me a Brake

Looking at the test results of the Police Vehicle Evaluation Program conducted annually by the Michigan State Police, we find that a Ford Crown Victoria can accelerate from 0 to 60 in 8.73 seconds. When the braking data is examined, you will find that the same vehicle can decelerate from 60 to 0 at an average of 27.26 ft/secĀ², which translates to a time of 3.2 seconds. The Crown Vic can stop from 60 MPH in about one third the time it takes to accelerate to 60 MPH. From the same report, look at the numbers for the Dodge Charger; it accelerates to 60 in 6.53 seconds and can stop from 60 in approximately three seconds. This data makes the point that the most powerful control on the vehicle is the brakes. Basically, the brakes produce larger changes in speed than the gas pedal.

Because the brakes have an enormous potential, they can be the producer of both good and evil. According to the Society of Automotive Engineers, most accidents start out with improper braking techniques.

Braking

Most drivers realize that the higher the car's speed, the more distance required to stop. What is surprising to many drivers is how much additional distance it takes to stop a vehicle with just a small increase in speed. The fact is that if you double your speed, you increase your stopping distance by a factor of four.

If you increase your speed from 40 to 44 mph, speed has increased by 10 %, but stopping distance has increased by 20 %.

If you increase your speed from 40 to 50 mph, speed has increased by 25 %, but stopping distance has increased by 50 %.

The numbers listed above are not affected by the method of braking used. It makes no difference if a driver brakes with their left foot--threshold brakes--or uses a parachute to stop. If the speed is doubled, the stopping distance increases by a factor of four. Bottom line: you cannot arbitrarily increase your speed; it's literally deadly.

As a side note--do not threshold brake with an ABS vehicle. With a vehicle equipped with ABS, press as hard as your foot can press and let the computer do its job.

The Connection

When confronted with an emergency, keep in mind that the gas pedal and the brake pedal are connected to each other. How much you can move the steering wheel depends on the speed of the vehicle. The lower the speed, the more you can move the steering wheel. It is important to understand that the sooner and harder you apply the brakes, the more you can turn the steering wheel.

With ABS, all it takes is that first hard application of the brakes, and as mentioned above, the computer takes over. But in order for the computer to operate at max efficiency, the brake pedal must be pressed as hard as possible. In many instances the driver does not accomplish this with the first application of the brakes; in fact they press semi-hard, and then increase the pedal pressure as the object they are trying to avoid gets bigger in the windshield.

In many emergencies, it is not only how quick you can stop, but how much speed can you take off the car as quickly as possible. As an example (the numbers that follow may not be completely accurate. There are many variables involved, but it is the theory that is important), if an ABS vehicle is traveling 50 mph and the brake pedal is applied as hard as possible, a half-second later that vehicle will be moving at the rate of 40 mph, and a second later that vehicle would be moving 28 mph. The point to be made is that the initial emergency occurred at 50 MPH; at that speed you have X amount of steering available before the vehicle will lose control. If the brakes are applied as hard as possible a half-second later, the vehicle is moving 40 mph, providing the driver with X plus steering to get out of trouble. A second later the vehicles is traveling 28 mph, giving the driver X plus plus steering to get out of trouble.

If you are an EVOC instructor, you can demonstrate this by pointing a radar gun at the vehicle as it enters the braking exercises, and notice how quick the speed drops. In fact, you can look at the radar gun and get an indication of how hard the student applied the brakes. If done properly, the speed indicated on the radar gun will drop significantly within the first second.

Look At This

A major component of braking to avoid an emergency has nothing to do with braking. It's all about where you look while the emergency is unfolding. Car manufactures have been studying this phenomenon for a while. Simply stated--your hands go where your eyes look. As soon as the emergency presents itself, look for a place to put the vehicle. Look where you want the vehicle to go, and your hands will follow your eyes. Many times the driver's eyes fixate on the object they are trying to avoid, and the result is that they drive into it.

EVOC instructors: this is a take away that you want all students to have when they leave your course. A good place to make the point is the accident avoidance/lane change etc. exercises. As soon as the command is given to go into a lane, the student needs to look where they want the car to go.

Summary

  1. Be careful about increasing speeds--for every 10% increase in speed, there is a 20% increase in stopping distance.
  2. When confronted with an emergency, press the brake pedal as hard as possible.
  3. The sooner and harder the brake is pressed, the more steering the driver will have available for driving out of the emergency.
  4. Look where you want to put the vehicle.

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