NC CDL General Knowledge flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Pre-trip inspection purpose

To confirm the vehicle is safe to operate before driving. Federal rule requires the driver to be satisfied that brakes, tires, lights, steering, and coupling are in safe condition.

Steering axle tread minimum

At least 4/32 inch of tread depth on every front (steering) axle tire. Other axles require at least 2/32 inch. Cuts exposing cords or sidewall bulges are defects.

Air brake leak-down limits

With the engine off and full pressure, pressure loss must be under 2 psi per minute for a single vehicle and under 3 psi per minute for a combination vehicle.

Low-air warning threshold

The low-air warning buzzer and light must activate by 60 psi. Spring brakes apply automatically at roughly 20 to 45 psi.

Total stopping distance formula

Perception distance plus reaction distance plus brake lag distance plus braking distance. Brake lag for air brakes is about 0.4 second, roughly 32 feet at 55 mph.

Backing a large vehicle

Back only when necessary, use a helper or get out and look, back toward the driver's side when possible, and back slowly while checking mirrors.

Double-clutching

Required in non-synchronized manual transmissions: press the clutch, shift to neutral, release the clutch, press it again, then select the next gear while matching engine rpm.

Downshift before a downgrade

Select a lower gear before starting down a long or steep grade. Do not coast in neutral or with the clutch depressed, and do not upshift on the grade.

Following distance rule

Allow one second per 10 feet of vehicle length at speeds under 40 mph, plus one second above 40 mph. A 60-foot vehicle needs 6 seconds under 40 mph and 7 seconds above.

Scanning ahead

Look 12 to 15 seconds ahead of the vehicle, about one city block in town and a quarter mile on the highway, to spot hazards early.

Blind spot rule

If you cannot see the commercial driver's mirror, that driver cannot see you. Large trucks have no-zone areas on both sides, directly behind, and in front.

Basic speed law

Speed must be reasonable and prudent for existing conditions, regardless of the posted limit. Rain, fog, ice, traffic, and road condition all require reduced speed.

Speed and braking distance

Braking distance grows with the square of speed. Doubling speed roughly quadruples braking distance, so higher speed greatly increases total stopping distance.

Engine braking on grades

Select a low gear before a downgrade and let the engine or retarder control speed. Do not ride the brakes, which can overheat and fade.

Space cushion

Keep at least one lane width on each side when possible, avoid driving beside another vehicle, and maintain following distance ahead and behind.

Stopped behind a vehicle

Leave enough space to see the rear tires of the vehicle ahead touching the road, so you can steer around it if it stalls.

Railroad crossing rule

Never stop on the tracks. If a gate comes down while you are on the crossing, drive through it rather than stopping on the tracks.

Hydroplaning speed

Hydroplaning can begin at highway speed with as little as 1/10 inch of water on the road. Reduce speed and avoid standing water.

Fog driving lights

Use low beams in fog, slow down, and increase following distance. High beams reflect off fog and reduce visibility, so never use them in fog.

Winter air system care

Drain air tanks daily to remove moisture that can freeze in the lines. Check antifreeze, battery, and the air dryer before cold-weather operation.

Brake failure response

Pump the brakes, downshift, apply the parking brake gradually, and look for an escape route. Do not panic or make sudden steering moves.

Tire blowout response

Hold the wheel firmly, do not brake hard, let the vehicle slow, and then pull off the road. Hard braking can cause a loss of control.

Skid recovery

Steer in the direction you want the front of the vehicle to go. Do not brake hard until the wheels regain traction, then straighten the wheel.

Reflective triangle placement

Set out triangles within 10 minutes of stopping: 10 feet behind the vehicle, 100 feet behind, and 100 feet ahead on a two-lane road.

Same gear up and down

Use the same gear going down a mountain grade that you used going up. Do not upshift on the grade; let engine braking control speed.

Escape ramp use

Escape ramps are for runaway vehicles that have lost braking. Do not stop or park on an escape ramp.

Low beam distances

Use low beams within 500 feet of oncoming traffic and within 200 feet when following another vehicle. High beams are for open road with no traffic.

Night stopping distance

Reduce speed at night so you can stop within the distance illuminated by your headlights. Overdriving headlights is a common night crash cause.

Cargo tiedown strength

Tiedowns must have a working load limit of at least 50% of the cargo weight, and the aggregate working load limit must be at least 1.5 times the cargo weight.

Hazmat shipping papers

Shipping papers must be within reach of the driver and include the proper shipping name, hazard class, and UN number for each hazardous material.

Air compressor cut-out

The governor cuts out the compressor around 120 to 125 psi and cuts it back in around 85 to 100 psi to maintain operating pressure.

Bus passenger safety

Do not move the bus until passengers are seated or holding handholds. Check the bus after each trip for sleeping passengers and hazards.