Alabama CDL General Knowledge cheat sheet

Speed must be reduced to a safe level whenever hazards, visibility, weather, road surface, or traffic conditions require it; the posted limit is a maximum, not a target.

Following distance rule for CMVs: one second per 10 feet of vehicle length at speeds under 40 mph, plus one extra second above 40 mph (a 60-foot rig needs 6 seconds below 40 mph, 7 seconds above).

Total stopping distance = perception distance + reaction distance + brake lag distance + braking distance.

At 55 mph a typical loaded tractor-trailer needs roughly the length of a football field plus to stop.

Space ahead is the most important space; if a tailgater appears, increase your own following distance so you can slow gradually.

Hydroplaning begins at speeds as low as 30 mph and is worsened by low tire tread, low tire pressure, and standing water.

Use four-way flashers when moving slowly (below 40 mph) on grades or highways where legal minimums are not met.

Stab braking (full brake application, release only if wheels lock) is used only for vehicles without ABS; with ABS apply firm continuous pressure and steer.

Cargo must be secured so it cannot leak, spill, blow off, or shift; shifting cargo can change axle weights and cause rollover or loss of control.

Aggregate working load limit of tiedowns must be at least 50% of the cargo weight for cargo not requiring special securement.

Minimum tiedowns: one for articles 5 feet or shorter and under 1,101 lb; two for articles longer than 5 feet but 1,101 lb or less; two for articles 5 feet or shorter and over 1,101 lb; three for articles longer than 5 feet and over 1,101 lb.

Tiedowns must be attached to the vehicle frame or mounting points, never to side rails, and must be tight with no knots in the web.

Front-end structure must be strong enough to contain cargo in a stop; rear-end structure must withstand a rear impact.

Check cargo and tiedowns within the first 50 miles and every 150 miles or 3 hours thereafter, whichever comes first.

Overloading an axle is illegal even if gross weight is legal; redistribute or remove cargo to bring each axle within its rating.

Any cargo that could be mistaken for a hazard requires placards per hazardous materials rules; never haul leaking or unsecured packages.

Air brake system has three braking systems: service brake (foot valve), parking brake (spring brakes), and emergency brake (spring brakes plus trailer protection valve).

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

The compressor builds pressure while the engine runs; the governor cuts out at about 125 psi and cuts in about 100 psi.

The alcohol evaporator, if equipped, is checked and filled each day in cold weather to prevent moisture from freezing in the system.

The air dryer removes moisture and oil before air reaches the tanks; drain the tanks daily to remove water and contaminants.

The safety valve on the first tank releases at about 150 psi to protect the system from overpressure.

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

To test for leaks: with engine off and full pressure, release the parking brake and watch for a drop of more than 3 psi in one minute (single vehicle) or 4 psi (combination).

The supply pressure gauge shows air available to the system; the application gauge shows air applied to the brakes.

Before backing, check that the trailer is straight behind the tractor; a combination cannot be backed if the trailer is at a sharp angle.

Rollover risk rises with speed in turns: reduce speed to about half the posted limit for the curve before entering it, and never brake hard while turning.

Trailer hand valve (trolley valve) should only be used to test trailer brakes, never for parking or normal stopping.

The tractor protection valve closes and applies trailer spring brakes if air pressure drops to 20-45 psi, preventing a breakaway.

The fifth wheel should be greased and the jaws closed and locked; test by pulling the tractor forward gently with the trailer brakes set.

Off-tracking means the rear wheels of a turning combination follow a shorter path; swing wide and check mirrors to avoid hitting curbs and signs.

When uncoupling: park, set trailer brakes, lower landing gear, disconnect air/electric lines, release fifth wheel jaws, then pull forward slowly.

Converter dollies must have their air lines and electrical cord properly connected; a dolly with a locked-up brake will cause tire drag and fire risk.

Rearward amplification means the last trailer swings wider than the tractor in a quick lane change; make smooth, gradual steering inputs.

Pre-trip inspection is required by federal regulation before each trip; the seven-step method covers engine compartment, walk-around, and in-cab checks.

Check engine oil, coolant, power steering fluid, and windshield washer fluid when the engine is cool and the vehicle is level.

Inspect belts for cracks, fraying, and proper tension (about 1/2 inch of play); check hoses for leaks and chafing.

Tire checks: tread depth of at least 4/32 inch for front tires and 2/32 inch for other tires; look for cuts, bulges, and proper inflation.

Brake check: with engine off, press the brake pedal and listen for air leaks; check slack adjuster free play and brake pad thickness.

Lighting check: headlights (high and low beam), turn signals, four-way flashers, clearance lights, brake lights, and reflectors must all work.

During the walk-around, check for leaks under the vehicle, loose lug nuts, cracked rims, and secure cargo.

In-cab check: seat belt, mirrors, horn, wipers, gauges, and steering wheel free play (should be no more than 10 degrees for power steering).

After-trip inspection reports are required for each vehicle operated and must note any defects found during the trip.

To start moving, release the parking brake only after the engine is running and air pressure is at least 100 psi.

Use the accelerator gently; a heavy foot on a loaded combination can cause wheel spin or a jackknife on slick surfaces.

Steering: keep both hands on the wheel, use push-pull steering to avoid crossing arms, and look well ahead in the direction of travel.

Backing: use a helper whenever possible, get out and check the area first, and back slowly; if you lose sight of the helper, stop immediately.

When turning, check mirrors for the rear of the trailer and swing wide enough to keep the trailer off curbs and signs.

Braking: use engine braking (downshifting) on long downgrades to avoid overheating the brakes; do not ride the brakes.

If the vehicle starts to skid, release the brakes, steer in the direction of the skid, and avoid hard acceleration.

Parking: set the parking brake, place the transmission in the lowest gear or park, and use wheel chocks on grades when required.

Manual transmissions in heavy trucks are usually non-synchronized; you must double-clutch to match engine and transmission speeds.

Upshifting: accelerate to the correct rpm, press the clutch, shift to neutral, release the clutch, press the clutch again, and shift into the next higher gear.

Downshifting: slow to the correct speed, double-clutch, and shift to the next lower gear to maintain control on grades.

Progressive shifting (shifting at lower rpm in each gear) saves fuel and reduces wear but requires practice.

Do not coast with the clutch in or the transmission in neutral; you lose engine braking and control.

If you miss a gear, do not force it; bring the vehicle to a stop and start again in the correct gear.

The tachometer should stay in the green band; lugging the engine below the band causes excessive wear and poor performance.

Automatic transmissions: use the selector for the correct range, and use engine braking or retarder on downgrades as instructed.

A hazard is any road condition, other driver, or situation that could require a change in speed or direction; scan 12-15 seconds ahead in urban areas and farther on open highway.

Look for clues: brake lights ahead, swerving vehicles, road signs, and pedestrians; act early rather than reacting late.

Check mirrors every 5-8 seconds and before changing lanes, slowing, or turning.

Use the 4-second rule for following distance in good conditions; increase to 8 seconds or more in rain, fog, or heavy traffic.

Watch for brake lights and turn signals of vehicles ahead; a vehicle that brakes suddenly may be preparing to turn or stop.

At night, use high beams when legal and look for reflections from animals' eyes; slow down when visibility is reduced.

Watch for road hazards: potholes, debris, construction zones, and standing water; reduce speed and increase following distance.

If a hazard is unavoidable, choose the safest option: slow down, steer around it if safe, or stop rather than swerve into traffic.

Texting while driving is illegal for commercial drivers and increases crash risk by up to 23 times compared with non-distracted driving.

Handheld phone use is prohibited for CMV drivers; use a hands-free device only when safe and legal.

Distractions include eating, drinking, adjusting the radio, and interacting with a GPS; set these before you start driving.

Looking away from the road for 2 seconds at 55 mph means traveling about 160 feet blind.

Fatigue is a major distraction; take breaks every 2 hours, and do not drive when drowsy.

Keep the cab clean and secure loose items so they do not roll around and distract you.

If you must use a device, pull over to a safe location and stop before using it.

Passengers and dispatchers should not distract the driver; use a co-driver or pull over to handle issues.

Never stop on railroad tracks; if traffic is backed up, wait until you can clear the crossing completely before proceeding.

At passive crossings (no gates or lights), slow down, look both ways, and listen before crossing; open the window to hear trains.

At active crossings, obey lights and gates; never drive around a lowered gate or past flashing lights.

Trains cannot stop quickly; a train traveling at 55 mph needs more than a mile to stop.

If your vehicle stalls on the tracks, get everyone out and away from the vehicle, then call 911 and the railroad emergency number posted at the crossing.

Do not shift gears while crossing tracks; a missed shift can leave you stalled on the rails.

Look for a second train after one passes; a second train may be coming on the other track.

If you are driving a bus or hazardous materials vehicle, you must stop at all railroad crossings (except exempt crossings) and check both ways.