Delaware CDL General Knowledge flashcards

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

Pre-trip inspection purpose

A systematic walk-around and in-cab check performed before each trip to confirm brakes, lights, tires, steering, coupling, and emergency equipment are safe and working, so defects are found before they cause a crash.

Three-point contact rule

When entering or exiting a truck cab, face the vehicle and keep three points of contact with the steps and handholds at all times; never jump, and never carry items that block your hands.

Governor cut-out pressure

The air compressor stops pumping when system pressure reaches roughly 120 to 125 psi; it resumes near 100 psi. Knowing this range lets you verify the compressor is cycling normally.

Low-air warning threshold

The warning buzzer and light must come on before air pressure drops below 60 psi. If it fails to activate, the vehicle is out of service until repaired.

Spring brake application range

With normal pressure lost, the parking spring brakes apply automatically somewhere between 20 and 45 psi; a lower or higher release point indicates an adjustment or leak problem.

Single vehicle leak rate

With a fully charged system, engine off, and brakes released, pressure loss must not exceed 3 psi in one minute for a single vehicle, or the system needs repair before driving.

Combination vehicle leak rate

For a tractor-trailer with a fully charged system, engine off, and brakes released, pressure loss must not exceed 4 psi in one minute; a larger drop means a leak must be fixed.

Applied brake leak test

Fully charge the system, shut off the engine, press and hold the brake pedal, and watch the gauge; a loss of more than 20 psi in one minute signals a serious leak.

Slack adjuster check

With the brakes released, pull the slack adjuster by hand; movement of more than about one inch at the push rod indicates excessive free play, and the brakes need adjustment or repair.

Brake lag distance

Air brakes do not apply instantly; about 0.4 seconds passes before braking begins at the wheels, adding roughly 32 feet at 55 mph to total stopping distance.

Total stopping distance

The sum of perception distance, reaction distance, brake lag distance, and actual braking distance; it grows with speed and weight, so a heavy truck at highway speed needs a very long clear path.

Four-second following rule

At speeds under 40 mph, stay at least four seconds behind the vehicle ahead; at higher speeds, add one second for each 10 feet of your vehicle length over 40 feet.

Perception distance

The distance traveled from the moment your eyes see a hazard until your brain recognizes it as a hazard; at 55 mph this alone can cover about 60 feet.

Reaction distance

The distance traveled from recognizing a hazard until your foot actually reaches the brake pedal; it depends on alertness and can be much longer when you are tired.

Downgrade gear selection

Before starting down a long or steep grade, shift into a gear low enough that engine braking holds your speed without using the brakes; do not shift while descending.

Snub braking technique

On a downgrade, apply the brakes firmly enough to reduce speed noticeably, then release them fully; this lets brakes cool between applications instead of overheating and fading.

Brake fade

Repeated or continuous braking overheats drums and shoes, reducing stopping power; if fade occurs, shift to a lower gear and use the brakes less, not harder.

Escape ramp use

A gravel or sand ramp built on steep downgrades for vehicles that lose braking; steer onto it, keep the vehicle straight, and expect deep, soft material that will stop you.

Railroad crossing stop rule

Buses carrying passengers and vehicles carrying hazardous materials must stop at railroad crossings unless the crossing is exempt; other drivers should slow, look, listen, and cross without shifting gears.

Right turn swing

Large vehicles may need to swing wide to the left before a right turn so the rear wheels clear the curb; watch the right side mirror and never let a car pass on the right during the turn.

Off-tracking

Rear wheels of a long vehicle follow a shorter path than the front wheels, so the trailer can cut the corner or strike a curb; allow extra room for turns and lane changes.

Blind spots around trucks

Large vehicles have blind spots on both sides, directly behind, and in front; if you cannot see the driver's face in the mirror, the driver cannot see you.

Hydroplaning speed

Tires can lose contact with a wet road at speeds as low as 30 to 35 mph, especially with worn tread or low pressure; slow down in rain and avoid standing water.

Skid recovery procedure

Stop braking, keep both hands on the wheel, and steer in the direction you want the vehicle to go; do not accelerate or brake hard until the tires regain traction.

Front wheel skid cause

Usually caused by driving too fast for conditions, oversteering, or braking too hard; the vehicle will not respond to steering until traction returns, so release the brakes and let it straighten.

Rear wheel skid cause

Often caused by accelerating too hard or braking unevenly on a slippery surface; the rear of the vehicle swings out, and steering into the skid helps bring it back in line.

Hazardous materials placards

Diamond-shaped signs placed on vehicles carrying regulated quantities of hazardous materials, identifying the hazard class so emergency responders know what is aboard.

Cargo securement rule

Cargo must be tied down with enough tiedowns and working load capacity to prevent shifting; aggregate working load limit must be at least half the weight of the cargo for most loads.

Tie-down count rule

Cargo up to 5 feet long needs at least one tie-down; cargo 5 to 10 feet needs two; longer cargo needs two plus one more for each additional 10 feet of length.

Front of load placement

Cargo should be placed against the front of the trailer or headboard when possible; this prevents forward shifting during sudden stops and keeps weight over the drive axles.

Axle weight limits

Federal limits are 20,000 pounds per single axle and 34,000 pounds per tandem axle group; exceeding them on a bridge formula road can result in fines and out-of-service orders.

Emergency equipment required

Most commercial vehicles must carry a fire extinguisher, spare fuses unless the vehicle has circuit breakers, and three reflective triangles for warning other traffic at a stop.

Triangle placement rule

Place warning triangles behind and ahead of a stopped vehicle: on a two-lane road, 10 feet and 100 feet behind and 100 feet ahead; on a divided highway, only the behind positions are used.