NC CDL General Knowledge key terms

A systematic walk-around check of tires, brakes, lights, fluids, couplings, and cargo done before driving. It catches defects that could cause a breakdown or crash and is required by federal and state rules.

A check with the engine off and system charged where you watch the pressure gauge for a specified drop over one minute with brakes applied and released. Excessive loss means the system must be repaired before driving.

The lever arm that links the brake chamber pushrod to the brake shoe. Its angle and travel show whether brakes are adjusted properly; too much pushrod travel means weak or delayed braking.

How far the pushrod extends when the brake is applied. Excess travel means the brake is out of adjustment, reducing stopping power and increasing stopping distance. It is measured during inspection and after adjustment.

A buzzer and light that activate before air pressure falls too low to stop safely, typically around 60 psi. If it comes on while driving, stop as soon as it is safe and find the leak.

An emergency and parking brake that applies by spring force when air pressure is released, either by the parking valve or by a major air loss. It fails safe, so the vehicle stops rather than rolls.

The pressure at which the compressor stops pumping, usually around 120 to 125 psi. Knowing the cut-out and cut-in pressures helps you judge whether the air system is cycling normally.

With the vehicle stationary, you set the parking brake and gently try to pull forward to confirm the brake holds. It verifies that the spring brakes or parking system actually engage.

A green light that has been green for a long time and may change before you reach the intersection. Cover the brake and prepare to stop instead of speeding up.

Total distance needed to stop, made up of perception distance, reaction distance, and braking distance. It grows with speed, weight, and poor traction, so it must be planned for well ahead.

The distance traveled from the moment a hazard appears until your eyes and brain recognize it. It is covered before you ever touch the brake and lengthens when you are tired or distracted.

The distance traveled between recognizing a hazard and actually applying the brake. It depends on alertness and technique, and it adds directly to total stopping distance.

The gap you keep behind the vehicle ahead, commonly one second for each ten feet of vehicle length at speeds under 40 mph, plus one extra second above that. It gives room to stop or steer around hazards.

The safety margin you maintain on all sides of your vehicle, including front, rear, and lateral gaps. Keeping it open gives you escape routes when traffic or road conditions suddenly change.

The blind spots around a large vehicle where a car driver cannot see you or be seen by you, including directly behind and alongside the trailer. Avoid lingering there and check mirrors before lane changes.

Setting flat and convex mirrors so you can see the sides and rear of the vehicle, including the trailer wheels and the lane beside you. Proper adjustment reduces blind spots and supports safe lane changes.

A curved mirror that widens your field of view but makes objects look smaller and farther away than they are. Use it for awareness, not for judging exact distance.

A shifting technique for non-synchronized transmissions: clutch in, shift to neutral, clutch out, clutch in again, then shift into the next gear. It matches engine and transmission speeds to allow a smooth shift.

Shifting without using the clutch by matching engine rpm to road speed and easing the lever between gears. It requires skill and is only appropriate for experienced drivers with unsynchronized transmissions.

Upshifting at progressively higher engine rpm as you go through the gears, which improves fuel economy and acceleration. It is used with some automated and manual transmissions under light loads.

A retarding device that uses engine compression to slow the vehicle without service brakes, helping control speed on downgrades. It is often restricted in residential areas by local signs.

A technique on long downgrades where you brake firmly to reduce speed, then release and let the engine brake hold it before repeating. It prevents continuous brake use and overheating.

Loss of braking power caused by overheated brake drums and linings, common when riding the brakes down a long grade. The pedal may feel normal while stopping power drops sharply.

An escape lane filled with gravel or sand on a steep downgrade for vehicles that lose braking. Steer into it early and straight; it is designed to stop a heavy vehicle safely.

A posted sign prohibiting engine-brake use in a specific area, usually because of noise ordinances. Violating it can bring a citation even when the brake would help control speed.

When water on the road lifts the tires off the surface so they lose contact and traction. It happens at speed with worn tires or deep water; ease off the accelerator and avoid hard braking.

What you do when tires lose grip: stop braking, steer in the direction you want the front to go, and avoid sudden inputs. Stay off the brakes until the tires regain traction.

The grip between tires and road surface that allows steering, braking, and acceleration. It falls on wet, icy, or gravelly roads and limits how hard you can safely maneuver.

A thin, nearly invisible layer of ice on the road, often in shaded spots, bridges, and overpasses. It looks like wet pavement and gives almost no traction, so reduce speed before reaching it.

Headlights that illuminate farther ahead and are used on dark roads with no oncoming traffic. Dim them within about 500 feet of an oncoming vehicle or when following closely to avoid blinding others.

Headlights aimed lower and shorter to avoid glare for oncoming and leading drivers. Use them in fog, rain, snow, and traffic, because high beams reflect back and worsen visibility.

The eye's ability to see in dim light, which is weaker than daytime vision and slow to recover after glare. It declines with age and fatigue, so slow down and increase following distance at night.

Tying down and containing a load so it cannot shift, spill, or fall off during transport. Federal rules set minimum tie-downs and working load limits based on cargo weight and type.

The combined strength of all tiedown assemblies used on a load, which must meet or exceed required minimums. It is calculated from each device's rated capacity, not from guesswork.

Placing cargo so weight is balanced across axles and kept within axle and gross weight limits. Poor distribution can overload tires, hurt steering, and make the vehicle unstable.

A diamond-shaped warning sign on a vehicle that identifies the hazard class of the cargo being carried. Placards are required above certain quantities and must match the material shipped.

The document describing hazardous materials in a shipment, including proper name, class, quantity, and emergency contact. It must be kept within reach and shown to inspectors or emergency responders.

A marked door, window, or roof hatch on a bus used to evacuate passengers quickly. Drivers must know how each one operates and explain them to passengers before a trip.

A marked line on a bus floor showing where standing passengers may not cross, keeping the aisle and driver's view clear. Passengers must stay behind it while the bus is moving.

The area where a bus stops to pick up or drop off riders, requiring careful approach, mirror checks, and attention to pedestrians. Stop close to the curb and signal before pulling out.