Mississippi CDL General Knowledge cheat sheet

Following distance rule for speeds under 40 mph: allow one second per 10 feet of vehicle length, plus one extra second; a 60-foot rig at 30 mph needs 7 seconds.

At speeds above 40 mph, add one additional second to the length-based following distance for every 10 mph over 40.

Total stopping distance = perception distance + reaction distance + brake lag distance + braking distance; perception and reaction together typically cover about 3/4 second at highway speed.

Speed and stopping: braking distance increases with the square of speed, so doubling speed roughly quadruples the distance needed to stop.

Hydroplaning begins at speeds around 30 mph with worn tires and can start at higher speeds with good tread; release the accelerator and avoid braking hard.

Use the 4-second hazard rule: when a hazard appears, count 4 seconds; if you reach it sooner, slow down and increase your following distance.

On downgrades, shift to a lower gear before starting down; brakes fade from overheating, so use engine braking and stab braking rather than continuous light pressure.

At night, dim high beams within 500 feet of an oncoming vehicle and within 200 feet when following another vehicle.

Railroad crossings: stop within 50 feet but not less than 15 feet from the nearest rail when required, and never stop on the tracks.

Cargo must be secured to prevent shifting; aggregate working load limit of tiedowns and securement must be at least 50% of the cargo weight.

Minimum tiedown counts: one tiedown for articles 5 feet or shorter and under 1,100 lbs; two tiedowns for articles longer than 5 feet or heavier than 1,100 lbs.

Front-end structure and rear-end structure plus one intermediate tiedown are required for cargo over 10 feet long when no header board or bulkhead is used.

Cargo must not obscure lights, reflectors, rear-view mirrors, or the license plate, and must not extend more than 3 feet beyond the front bumper or 4 feet beyond the rear.

Projecting loads: a red or orange flag at least 18 inches square marks the end of loads extending 4 feet or more beyond the rear or sides.

Legal gross weight is the lowest of the posted bridge/road limit, the tire limit, the axle limit, and the vehicle registration or manufacturer rating.

Axle weight limits are set per axle and per axle group; overloading an axle is illegal even when total gross weight is under the limit.

Before driving, inspect cargo securement, and re-check tiedowns within the first 50 miles and every 150 miles or 3 hours thereafter.

Before loading, check that baggage and freight are secure and that no hazardous materials are aboard unless properly permitted and marked.

Standees are prohibited on buses with a gross vehicle weight rating over 10,000 lbs; passengers must remain seated while the bus is moving.

Do not allow riders in a towed trailer or in the space behind the last seat unless the vehicle is designed for them.

At each stop: announce the stop, check mirrors, load and unload only at designated safe locations, and count passengers when boarding and leaving.

After every stop, account for all passengers; do not move until every rider is seated or safely standing and holding a handrail.

A bus may never be left unattended with passengers aboard; if you must leave, shut off the engine, set the parking brake, and remove the key.

On a bus, the emergency exit doors and windows must be checked for operation before each trip and kept clear of baggage.

When stopping to load or unload, pull completely off the roadway; if that is impossible, use warning devices such as flashers and triangles.

Air brake system pressure must build from 85 to 100 psi within 45 seconds at fast idle during the compressor check.

Leak test: with the engine off and brakes released, pressure loss must not exceed 3 psi in one minute; with the brakes applied, loss must not exceed 4 psi in one minute.

Low-air warning must activate before pressure drops below 60 psi; the spring brakes must fully apply between 20 and 45 psi.

The governor cuts the compressor in around 100 psi and out around 125 psi; normal operating range is roughly 100-125 psi.

Air brake lag: allow about one second of lag time before brakes take hold, so stopping distance is longer than with hydraulic brakes.

Use stab braking on long downgrades: apply the brakes fully when speed reaches about 5 mph over your safe speed, hold until speed drops to about 5 mph under, then release.

Never push the brake pedal down and hold it on a long downgrade; continuous application overheats drums and causes brake fade.

The safety valve releases at about 150 psi to protect the system; if it discharges, the system has a problem and must be checked.

Before driving, check that the parking (spring) brake knob pops out and the vehicle does not move when you test the brakes at low speed.

Inspect the coupling: the kingpin must be fully seated in the fifth wheel, the locking jaws must close around the kingpin, and the release lever must be in the locked position.

Tug test: after coupling, pull gently against the trailer with the trailer brakes set to confirm the coupling holds before raising the landing gear.

Check the air lines and electrical cord for chafing and secure connection; the emergency air line must be connected or the trailer brakes will not release.

Bobtail (tractor alone) braking distance is shorter than with a loaded trailer, so allow more following distance when loaded.

Off-tracking: the rear wheels of a combination vehicle follow a shorter path than the front wheels; swing wide on turns and watch the trailer in the mirrors.

When turning, turn the steering wheel more than you would in a car and check the trailer wheels; the trailer can clip curbs or vehicles on the inside.

Rollover risk rises with a high center of gravity and speed in turns; slow down before curves and avoid sudden steering inputs.

Before backing, get out and check the area, use a helper if possible, and back slowly; if you lose sight of the helper, stop immediately.

Converter dollies must have their air lines and electrical cord connected, and the dolly must be secured to the first trailer before coupling the second.

Check that the safety chains are crossed under the coupling and that the dolly's spring brakes release properly when air is supplied.

Doubles and triples have more articulation points, so they require wider turns and more room to stop than a single trailer.

The rear trailer tends to swing out and off-track more sharply; watch the last trailer's wheels in turns and when changing lanes.

Order of coupling: connect the dolly to the first trailer, then back the second trailer to the dolly; check each coupling with a tug test.

Shut-off valves: the trailer air supply valves at the rear of each unit must be open for the following trailer to receive air.

Inspect glad hands and couplers for damage and ensure no air leaks at each connection before driving.

Uncoupling: set the parking brakes, chock wheels, disconnect the air lines and electrical cord, then lower the landing gear before pulling out.

Liquid surge: a partially filled tank has more free surface effect, so the load shifts and can push the vehicle; keep tanks full or drained when possible.

High center of gravity and liquid movement make tank vehicles more prone to rollover; slow down well before curves and avoid abrupt steering.

Baffles divide the tank to reduce surge but do not eliminate it; smooth bore tanks have the strongest surge.

Check that hatches are closed and secure before moving, and confirm the tank's vents are open as required for the product.

Tank vehicles hauling flammable liquids must have the proper placards, and the driver must know the emergency response information for the product.

Stopping distance increases because of the weight and surge; allow extra following distance and brake earlier and more gently.

Before loading or unloading, set the parking brake, chock the wheels, and bond/ground the vehicle when handling flammable liquids.

Check the tank, hoses, and valves for leaks before and after loading, and never smoke or use open flame near a tank vehicle.

A hazardous materials endorsement (H) is required to drive a vehicle carrying placarded amounts of hazardous materials, and a background check applies.

Placards must be displayed on both sides and both ends of the vehicle for each hazard class carried in the required quantity.

Shipping papers must be within reach while driving, kept in a pouch on the driver's door or in clear view, and include the proper shipping name, hazard class, and UN number.

Emergency response information must accompany the shipping papers and include the guide number or response guide reference.

Never smoke or carry fire near hazardous materials, and keep the engine off during loading and unloading unless the product requires it.

Parking rules: do not park within 5 feet of a roadway, and never park near an open flame, bridge, tunnel, or crowded place unless attended.

Report spills, leaks, or accidents involving hazardous materials immediately to the proper authorities, and stay clear of vapors and fire.

The hazardous materials endorsement requires a knowledge test and a TSA security threat assessment; it is not issued automatically with the CDL.

School bus drivers must use the 8-light warning system: amber lights warn of a stop, and red lights plus the stop arm signal children are crossing.

Stop at least 10 feet from the nearest rail at railroad crossings, open the door, and check both ways before crossing.

Loading and unloading: stop with the bus's left side no more than the specified distance from the curb, set the parking brake, and place the transmission in neutral or park.

Students must cross in front of the bus, never behind it, and the driver must watch them until they are clear of the danger zone.

The danger zone extends about 10 feet around the bus; students within it are hard to see, so use mirrors and count students at every stop.

A school bus may not be left unattended with students aboard; if you leave, shut off the engine, set the brake, and remove the key.

Use the pre-trip inspection to check the stop arm, flashing lights, crossing gate, and emergency exits for proper operation.

When a school bus is stopped with red lights flashing, traffic in both directions must stop unless separated by a median or barrier.

Pre-trip inspection covers engine compartment, cab/cab checks, walk-around inspection, and brake checks; the walk-around covers lights, tires, and securement.

Tire checks: tread depth of at least 4/32 inch on front tires and 2/32 inch on other tires, with no cuts, bulges, or exposed cords.

Check that all lights work: headlights, high beams, turn signals, brake lights, clearance lights, and reflectors on the tractor and trailer.

Engine compartment checks include oil level, coolant, power steering fluid, and belt condition; never remove a radiator cap while the engine is hot.

Brake check: test the parking brake, service brake, and (for air brakes) the low-air warning and leak rate before driving.

Check the fifth wheel, kingpin, and safety latches on the coupling, and confirm the trailer landing gear is fully raised before moving.

Steering and suspension: check for loose or missing parts, cracked or bent components, and proper fluid levels in the steering system.

During the trip, re-check cargo securement, tires, and lights at each stop; report defects that affect safe operation before continuing.

Start the engine and let air pressure build to normal before releasing the parking brake; for air brakes, wait until the low-air warning stops.

Use the clutch and throttle smoothly when starting from a stop; on a hill, use the parking brake or clutch friction point to prevent rollback.

Steering: hold the wheel with both hands, look far ahead, and make smooth corrections; avoid oversteering at highway speed.

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

Shifting: do not coast in neutral or with the clutch in; use the correct gear for the speed and grade, and never skip gears when downshifting.

Speed control on curves: slow down before entering the curve, maintain speed through it, and accelerate gently on the way out.

Use turn signals well in advance, check mirrors, and make sure the lane is clear before changing lanes or turning.

Parking: set the parking brake, place the transmission in the proper gear or park, turn the wheels toward the curb on a downgrade, and shut off the engine.