CDL General Knowledge in 3 Minutes

Transcript

The General Knowledge test is the one every commercial driver license applicant takes, no matter which class or endorsements they want. It is built on your state's commercial driver manual, and most of it comes down to a handful of safety ideas. If you truly understand why these rules exist, the questions become much easier.

Start with the pre-trip inspection. Its purpose is simple: find problems before they cause a crash or a breakdown on the road. You check tires, brakes, lights, steering, suspension, fluid levels, coupling devices, and emergency equipment, using the same order every time so nothing gets skipped. Inspection does not stop when you pull out, either. You keep watching gauges and mirrors while driving, and you check again after the trip.

Next, stopping distance. Total stopping distance has three parts. Perception distance is how far you travel while your brain recognizes a hazard. Reaction distance is how far you travel while your foot moves to the brake. Braking distance is how far you travel once the brakes are actually working. Here is the key fact: braking distance grows much faster than speed. Double your speed, and it takes roughly four times the distance to stop. A heavy truck also needs more distance than a car, so speed is the easiest risk you control.

Third, following distance. The manual gives a rule of thumb: at least one second for every ten feet of vehicle length at speeds below forty miles per hour. Above forty, add one more second. So a forty foot truck at thirty five miles per hour needs four seconds. The same truck at fifty five needs five seconds. To measure it, wait for the vehicle ahead to pass a fixed point, like a shadow or a sign, then count one thousand and one, one thousand and two, until your front bumper reaches it.

Finally, space management and rollover. Keep space ahead, behind, to the sides, overhead, and below, because you need an escape route and clearance for bridges and low wires. And remember that a loaded truck has a high center of gravity. Taking a curve or ramp too fast, or turning sharply, can tip it over, even at speeds well below the posted limit. Keep the cargo low and centered, and slow down before the curve, not in it.

So here is your recap. Inspect before, during, and after every trip. Stopping distance is perception plus reaction plus braking, and doubling speed quadruples braking distance. Use one second per ten feet, plus one over forty. And slow down before curves.