CDL cheat sheet

CDL threshold: a gross combination weight rating of 26,001 lb or more with a towed unit over 10,000 lb; any vehicle designed for 16 or more passengers; or any vehicle carrying placarded hazardous materials.

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

At 55 mph, perception distance is about 60 feet and reaction distance is about 60 feet before the brakes begin to apply.

Following distance rule: one second per 10 feet of vehicle length below 40 mph, plus one additional second above 40 mph, so a 60-foot rig needs 7 seconds.

Minimum tire tread depth: 4/32 inch on front tires, 2/32 inch on all other tires.

The legal BAC limit for operating a CMV is 0.04; refusing a required test puts the driver out of service.

GVWR is the maximum loaded weight of a single vehicle set by the manufacturer; GCWR covers the power unit plus towed vehicles.

Engine retarders must be switched off on wet, icy, or slippery surfaces because drive-wheel braking can start a skid.

Mirror checks must show the rear tires and about 200 feet (or 4 seconds) of road behind the vehicle before any lane change.

Order of components: compressor, governor, reservoirs, safety valve, foot valve, brake chambers, slack adjusters.

The governor cuts the compressor in at about 100 psi and out at about 125 psi.

The reservoir safety valve opens at about 150 psi to prevent overpressurization.

A low pressure warning light or buzzer must operate before pressure falls below 60 psi.

Spring brakes begin to apply automatically at roughly 20 to 45 psi.

Static leak test (fully charged, engine off, brakes released): loss under 3 psi per minute for a single vehicle and under 4 psi per minute for a combination.

Applied-brake leak test: loss under 4 psi per minute for a single vehicle and under 6 psi per minute for a combination.

Compressor build rate: 50 to 90 psi within 3 minutes for a single system; 85 to 100 psi within 45 seconds for a dual system.

Pushrod travel beyond the adjustment limit with brakes applied means the brakes are out of adjustment.

Coupling checks: no gap between the upper and lower fifth wheel, locking jaws closed around the kingpin, and a tug test with trailer brakes locked.

Red glad hand is the emergency (supply) line; blue glad hand is the service (control) line.

The tractor protection valve closes on trailer breakaway or air line separation and keeps tractor air from escaping.

The trailer hand valve (trolley valve) is for testing trailer brakes only and is never a parking brake.

Bobtailing lengthens stopping distance because the tractor is light and only its own brakes work; brake earlier.

Off-tracking: rear wheels follow a path inside the front wheels, so the front must clear the corner before the turn is completed.

Close the trailer shut-off valves and chock the wheels before uncoupling.

Over-braking an empty trailer can lock its wheels and cause a jackknife; brake pressure must match the load.

Trailer air lines need enough slack to turn and back without kinking, dragging, or pulling apart.

A converter dolly has one or two axles, its own fifth wheel, a pintle eye, and safety chains, and normally carries no brakes itself.

Coupling order for doubles: rear trailer to the dolly first, then the dolly to the first trailer, with a tug test at each coupling.

Rearward amplification: the last trailer swings widest and travels fastest through a turn, so speeds must be lower.

Close each trailer's air line shut-off valves before uncoupling so the trailer keeps its air and spring brakes stay applied.

Chock the wheels of any trailer being left before releasing its coupling.

Test each trailer's brakes separately by opening one shut-off valve at a time.

Off-tracking grows with every added trailer, so turns must be wider than with a single trailer.

Dolly safety chains are crossed under the dolly tongue and hooked to the towing trailer.

Because dollies are unbraked, stopping distance depends entirely on the tractor and trailer brakes.

Surge is liquid moving inside a partly filled tank during starts, stops, and turns, shifting weight and lengthening stopping distance.

Baffles reduce surge but never eliminate it.

Outage is the empty space left in a tank for expansion; filling beyond it can rupture the tank.

Smooth-bore (unbaffled) tanks require lower speeds and often a special permit.

A tank load raises the center of gravity, increasing rollover risk on curves and ramps.

Bulkheads divide a tank into compartments, and each compartment is loaded and checked separately.

Before loading, check the dome cover, gasket, and valves; after loading, check the dome and outlets for leaks.

Brake early and gently with a partial load so the liquid does not push the vehicle forward.

Check that tank vents are clear and the tank is not overfilled before moving.

Nine hazard classes: 1 explosives, 2 gases, 3 flammable liquids, 4 flammable solids, 5 oxidizers and organic peroxides, 6 toxic and infectious substances, 7 radioactive, 8 corrosive, 9 miscellaneous.

Placard thresholds: 1,001 lb aggregate gross weight for Table 1 materials and 2,205 lb for Table 2 materials; some materials need placards in any amount.

Bulk packages carry placards on both sides and both ends.

Shipping papers with emergency response information must be kept within the driver's reach.

Never park a placarded vehicle within 5 feet of the traveled roadway, and keep it away from open fires and congested areas.

No smoking within 25 feet of a placarded vehicle during loading, unloading, or fueling.

Stop before railroad crossings and do not shift gears while crossing the tracks.

Never enter a tunnel posted against hazardous materials; routes must avoid restricted tunnels and bridges.

Fuel with the engine off and the parking brake set.

Standee line: no passenger may ride forward of it while the bus is moving.

Railroad crossings with passengers aboard: stop 15 to 50 feet from the nearest rail, listen, and cross only when clear.

Count passengers off the bus and check the seats for sleeping riders before leaving the bus unattended.

Do not fuel a bus while passengers are aboard.

Emergency exits include the rear door, side windows, and roof hatches.

Some buses have a brake-door interlock that prevents the bus from moving with the door open.

Load and unload only at designated stops, and watch for riders crossing in front of the bus.

Standees are not allowed forward of the standee line or on buses not rated for standing passengers.

Use four-way flashers when stopped to load or unload where permitted.

The seven-step inspection covers the engine compartment, walk-around items, brake checks, and lights, and takes about 15 to 30 minutes.

Pre-trip items include fluid levels, belts, hoses, steering, suspension, tires, wheels, lights, reflectors, and coupling devices.

Three brake tests: parking brake, service brake, and the air or hydraulic system check.

Tread depth minimums are 4/32 inch at the front and 2/32 inch at other positions; look for cuts, bulges, and exposed cords.

Skid recovery: steer in the direction the front of the vehicle should go and ease off the brakes.

Before a downgrade, shift into a lower gear and use engine braking, applying the service brakes hard enough to feel slowing, then releasing.

Hydroplaning: ease off the accelerator and avoid hard braking until the tires regain contact with the road.

Texting and hand-held device use are prohibited for CMV drivers while driving.

At night, do not overdrive the headlights; drive so you can stop within the distance you can see.