Alabama CDL General Knowledge flashcards

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

Following distance rule

For CMVs, allow one second per 10 feet of vehicle length below 40 mph, plus one extra second above 40 mph. A 60-foot rig needs 6 seconds below 40 mph and 7 seconds above.

Total stopping distance

The sum of perception distance, reaction distance, brake lag distance, and braking distance. At 55 mph a loaded tractor-trailer needs roughly the length of a football field plus to stop.

Hydroplaning speed

Hydroplaning can begin at speeds as low as 30 mph, especially with low tire tread, low pressure, or standing water. Reduce speed and avoid sudden braking when water is present.

Stab braking

A technique for vehicles without ABS: apply the brakes fully, release only if the wheels lock, and reapply. With ABS, apply firm continuous pressure and steer instead.

Securement working load

Tiedowns must have an aggregate working load limit of at least 50% of the cargo weight for cargo not requiring special securement. Tiedowns must be tight and attached to the frame.

Minimum tiedown count

One tiedown for articles 5 feet or shorter and under 1,101 lb; two for longer or heavier articles; three for articles longer than 5 feet and over 1,101 lb.

Cargo inspection interval

Check cargo and tiedowns within the first 50 miles and every 150 miles or 3 hours thereafter, whichever comes first. Shifting cargo can change axle weights and cause rollover.

Axle weight limit

Overloading an axle is illegal even when gross weight is legal. Redistribute or remove cargo to bring each axle within its rated capacity before driving.

Air brake warning pressure

The low-air warning must activate by 60 psi, and the spring brakes must apply when pressure drops to 20-45 psi. Normal operating pressure is 100-125 psi.

Slack adjuster free play

Slack adjusters must have no more than 1 inch of free play at the pushrod. Excessive play means the brakes are out of adjustment and must be repaired before driving.

Air leak test

With the engine off and full pressure, release the parking brake and watch for a drop of more than 3 psi in one minute for a single vehicle, or 4 psi for a combination.

Safety valve setting

The safety valve on the first air tank releases at about 150 psi to protect the system from overpressure. The governor normally cuts out near 125 psi.

Tractor protection valve

This valve closes and applies the trailer spring brakes when air pressure drops to 20-45 psi, preventing a breakaway and loss of trailer braking.

Off-tracking

The rear wheels of a turning combination follow a shorter path than the front wheels. Swing wide and check mirrors to avoid hitting curbs, signs, and other vehicles.

Rearward amplification

In a quick lane change, the last trailer swings wider than the tractor. Make smooth, gradual steering inputs to avoid rollover or loss of control.

Fifth wheel test

After coupling, set the trailer brakes and pull forward gently. If the tractor moves without resistance, the jaws are not locked and the coupling is unsafe.

Tire tread minimum

Front tires need at least 4/32 inch of tread depth; other tires need at least 2/32 inch. Check for cuts, bulges, and proper inflation during the pre-trip inspection.

Steering free play

With power steering, the steering wheel should have no more than 10 degrees of free play. Excessive play indicates wear and must be repaired before driving.

Pre-trip inspection steps

The seven-step method covers the engine compartment, walk-around checks, and in-cab checks. Federal regulation requires a pre-trip inspection before each trip.

Starting air pressure

Release the parking brake only after the engine is running and air pressure is at least 100 psi. Low pressure can prevent the spring brakes from releasing fully.

Skid recovery

If the vehicle starts to skid, release the brakes, steer in the direction of the skid, and avoid hard acceleration. Do not lock the brakes or oversteer.

Backing safety

Use a helper whenever possible, check the area before backing, and back slowly. If you lose sight of the helper, stop immediately and reestablish contact.

Engine braking on grades

Downshift and use engine braking on long downgrades to avoid overheating the brakes. Do not ride the brakes continuously, which can cause fade or failure.

Double-clutching

Non-synchronized heavy truck transmissions require double-clutching: press the clutch, shift to neutral, release, press again, and shift to the next gear.

Progressive shifting

Shifting at lower rpm in each gear saves fuel and reduces wear. Keep the tachometer in the green band and avoid lugging the engine below it.

Missed gear recovery

If you miss a gear, do not force it. Bring the vehicle to a stop and start again in the correct gear to avoid transmission damage or loss of control.

Coasting prohibition

Do not coast with the clutch in or the transmission in neutral. You lose engine braking and control, especially on downgrades and slick surfaces.

Hazard scanning distance

Scan 12-15 seconds ahead in urban areas and farther on open highway. Look for brake lights, swerving vehicles, road signs, and pedestrians to act early.

Mirror check interval

Check mirrors every 5-8 seconds and before changing lanes, slowing, or turning. Use the 4-second following rule in good conditions and 8 seconds or more in bad weather.

Texting crash risk

Texting while driving is illegal for commercial drivers and increases crash risk by up to 23 times. Handheld phone use is prohibited; use hands-free devices only when safe.

Two-second glance distance

Looking away from the road for 2 seconds at 55 mph means traveling about 160 feet blind. Set radios, GPS, and food before you start driving.

Railroad crossing stall

If your vehicle stalls on the tracks, get everyone out and away, then call 911 and the railroad emergency number posted at the crossing. Never stop on the tracks.

Train stopping distance

A train traveling at 55 mph needs more than a mile to stop. Trains cannot stop quickly, so never try to beat a train at a crossing.