VEHICLE DYNAMICS - Braking

Tony Scotti

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 –there are training organizations that are teaching threshold braking with an ABS vehicle - 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.

LOOK WHERE YOU WANT TO GO
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 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 they drive into it. By the way, this is not as easy as it sounds.

SUMMARY

1. Be careful about increasing speeds – for every 10% increase in speed it is a 20% increase in stopping distance.
2. With an ABS vehicle, when confronted with an emergency press the brake pedal as hard as possible.
3. The sooner and harder the brake is pressed the the lower the speed and the lower the speed the more you can move the steering wheel
4. Look where you want to put the vehicle.

Any questions or comments contact me at tonyscotti@securitydriver.com