The ABCs of Precision Driving

It's critical to understand the forces that interact to influence vehicle control.


Most officers have been through some sort of driver training, either in the academy, or as part of an in-service class. While academy training is often looked upon as so basic as to be almost useless in the real world, one place where that is absolutely not the case is in driver training.

Academy driver training is usually built around a defensive driving model, and is perhaps better referred to as precision driving. Most of the recruits that enter an academy have just a few years of driving experience under their belts, along with a high school driver's education class that may or may not have done a good job of addressing the basics.

Because recruits will soon be "out there" in the real police world, and will be operating a vehicle on a daily basis, academy driving instructors must do what they can to ensure that graduating recruits have a solid grounding in basic driving skills. In order to do that, they must address the fundamentals of vehicle operation. Here's how we teach it at our academy.

The ABC Approach to Driver Training

A vehicle is only designed to do three things. First, it has to "go," and that involves acceleration. Here we're not just talking about an increase in speed, which is the common usage of the term. In order to keep a vehicle moving down the roadway, constant acceleration force must be applied to the wheels; otherwise the vehicle will roll to a stop. Acceleration is the "A" in ABC.

If it's going to "go," then it has to "stop," and in the case of a vehicle, that's accomplished through braking force. Braking occurs in two ways: One is the natural braking that occurs through application of physical laws and natural forces--think gravity, inertia, and Newton's laws--and the other is the active braking that occurs when a driver steps down on a vehicle's brake pedal.

When active braking occurs, friction develops (this actually happens during "natural" braking, as well, but we'll focus here on the active type). Friction occurs in two general areas: One is within the braking system itself--between the pads and rotors, or between the shoes and drums--and the other is between the tire and the road surface.

There is a relationship between the friction that develops at these two points, and that relationship, or ratio, must be balanced. If too much friction develops in the braking system, the vehicle may begin to skid, or the anti-lock braking system may take over. If not enough friction develops in the braking system, the vehicle won't slow down soon enough, and the vehicle might hit whatever object the driver was trying to avoid.

A driver learns how to manage this braking ratio through experience, and must constantly monitor it, as each vehicle's equipment and each roadway surface condition will require an adjustment on the driver's part. Braking, then, is the "B" in ABC.

The third thing a vehicle is designed to do is to turn, or to corner. Anytime a vehicle deviates from a straight path of travel--be it forward or reverse--cornering force develops.

When engaging in precision or performance driving, an officer will typically be interested in arriving as quickly and safely as possible. This will usually translate to the way a driver manages his or her vehicle's cornering. Often drivers use a technique commonly referred to as "apex cornering." Most drivers do this, and it is sometimes referred to--or thought of--as "straightening out the curves." Vehicles that are apex cornering will use as much of the roadway as they can, while maintaining a safe path of travel. Thus, if a driver can see around a curve or a corner, he or she will cut across the corner, thereby straightening out the curve, and shortening the distance the vehicle must travel to get around the curve (the shortest distance between two points is a straight line, and the same holds true for the shortest distance around a curve).

Cornering does not occur by itself; it is done in tandem with acceleration or braking. Cornering is the "C" in ABC.

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