NY CDL Doubles and Triples cheat sheet

Coupling order: set trailer brakes, back under slowly, stop when the fifth wheel touches the trailer apron, then check that the kingpin is centered in the throat of the fifth wheel before tugging.

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After the tractor is under the trailer, raise the landing gear fully before the tug test; a loaded trailer's gear can be damaged or the tractor can be lifted if you pull forward on extended legs.

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Tug test: pull forward gently in a low gear with the trailer brakes still set; the tractor should not move. If it moves, the jaws are not locked - stop and recheck.

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Lock the fifth wheel release lever and insert the safety cotter pin; a lever that can be flipped by hand without pulling the pin means the lock is not secure.

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Connect the air lines (blue = service/emergency, red = supply) and the electrical cord, then check that lines are not crossed, kinked, or dragging on the catwalk.

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Uncoupling order: park on firm level ground, set the trailer brakes (spring brakes), lower the landing gear to the ground, then release the fifth wheel and pull forward slowly.

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Before pulling out from under the trailer, disconnect the air lines and electrical cord and secure them so they do not catch on the trailer or the tractor frame.

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After uncoupling, lower the landing gear so the trailer rests on the gear, not on the tractor frame; chock the wheels if the trailer is not on level ground.

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Check the fifth wheel plate is greased and the jaws are open before coupling; a dry or misaligned plate prevents full lock and causes false coupling.

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Verify the trailer is at the correct height: the trailer apron should contact the fifth wheel plate and lift it slightly, so the kingpin slides into the throat.

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After coupling, check the gap between the tractor frame and the trailer; a visible gap or daylight at the fifth wheel means the kingpin is not fully seated.

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Set the trailer brakes before backing under; if the trailer rolls during coupling, the landing gear or the tractor can be damaged.

Doubles/triples require a converter dolly between the first and second trailer; the dolly has its own fifth wheel, kingpin, and air/electrical connections that must be checked separately.

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Inspect every unit in the combination, not just the tractor: each trailer's brakes, lights, tires, mud flaps, and the dolly's connections must be checked before departure.

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Check that the converter dolly's air lines are connected in the correct order: the dolly's emergency (blue) line goes to the tractor's emergency line, and the service (red) line goes to the service line.

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The rear trailer of a set must have its own brake system, and the combination must have a breakaway valve that applies the trailer brakes if the lines separate.

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Check the coupling between each trailer and the dolly: the same tug test and fifth-wheel lock check applies to every connection, not just the tractor-to-first-trailer.

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Verify that the dolly's safety chains or the trailer's safety chains are attached and crossed where required, so the dolly does not drop to the pavement if the coupling fails.

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Check that the rear trailer's lights and turn signals work from the tractor's controls, since the electrical cord runs through the dolly and can be pinched or disconnected.

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Confirm the total length and weight of the combination against the permit and state limits; doubles/triples often require a special permit and route restrictions.

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Inspect the dolly's pintle hook or coupling and the drawbar for cracks, wear, or missing pins; a worn pintle hook allows the dolly to separate under load.

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After coupling the dolly, check that the dolly's landing gear or support legs are raised and secured so they do not drag or catch on the road.

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Check the air pressure builds and holds on the whole combination: with the engine off and brakes released, pressure should not drop more than a few psi per minute.

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Walk the full length of the combination after coupling; a missed connection on the rear trailer is invisible from the cab until it fails.

Color code: blue = service/emergency (trailer brake) line, red = supply (emergency) line; on a dolly, the lines must be matched so the tractor's supply feeds the trailer's supply.

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Check that air lines are not crossed: a crossed supply and service line causes the trailer brakes to release when you apply the tractor brakes, or to drag constantly.

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Inspect the gladhands for a good seal and the coupler gaskets for cracks; a leaking gladhand causes slow pressure loss and weak trailer braking.

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Check the electrical cord for a secure plug, a good seal, and no exposed wires; a loose plug causes intermittent lights and can trigger a turn-signal failure.

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Route the air lines and cord so they do not drag on the catwalk, rub against the frame, or get pinched between the tractor and trailer during turns.

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After connecting, listen for air leaks at the gladhands and at the dolly connections; a steady hiss means a bad seal or a partially engaged coupler.

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Test the trailer brakes from the cab: with the tractor brakes released, apply the trailer hand valve and confirm the trailer brakes set; then release and confirm they release.

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Check the breakaway system: the trailer's breakaway valve should apply the trailer brakes if the air lines separate, and the tractor protection valve should close off the tractor's air supply.

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With the engine off, check that the combination holds air pressure; a drop of more than about 3 psi per minute indicates a leak in the lines or connections.

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Inspect the cord and lines at the dolly connection, since that is where the lines flex most and where chafing or a pulled plug is most likely.

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Confirm that the electrical cord is long enough to allow full turns without pulling tight; a tight cord can unplug or break during a sharp turn.

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Check the lines after the first few miles of a trip, since vibration and turns can loosen a gladhand that felt tight at the dock.

Stopping distance increases with the number of trailers and with weight; allow a following distance of at least one second per 10 feet of vehicle length plus one second, and add more in poor conditions.

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Use the trailer hand valve (spike) only to test trailer brakes, never to park or to hold the vehicle; it can cause a jackknife if used while moving.

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Brake smoothly and progressively; sudden hard braking with multiple trailers causes the rear trailer to push the tractor and can cause a jackknife or a trailer swing.

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The rear trailer's brakes may apply slightly later than the tractor's due to air line length; allow extra distance and avoid tailgating so the lag does not cause a collision.

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On downgrades, select a low gear before starting down and use engine braking; do not ride the brakes, which can fade and leave the combination without stopping power.

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If the combination starts to jackknife under braking, release the brakes and steer in the direction the tractor is skidding to regain control, then reapply gently.

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With doubles/triples, the rear trailer can swing out during hard braking; keep the combination straight and brake in a straight line whenever possible.

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Check the trailer brake adjustment and slack adjusters during inspection; a trailer with poorly adjusted brakes does more of the stopping work on the tractor and increases stopping distance.

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Use the tractor protection valve and trailer air supply correctly: if the trailer air pressure drops, the trailer brakes should apply automatically, so a low-pressure warning is a stop signal.

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When stopping, apply the brakes early and lightly and keep the combination straight; a stop on a curve or slope with multiple trailers can cause the rear trailer to roll or swing.

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The heavier the load, the longer the stopping distance; a fully loaded triple combination can take much longer to stop than an empty one, so increase following distance accordingly.

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After stopping, set the parking brakes on the tractor and the trailer, and chock the wheels if parked on a grade; a multi-trailer combination can roll if only the tractor brakes are set.

Offtracking: the rear wheels of the last trailer follow a shorter path than the tractor's front wheels, so the rear trailer cuts the corner and can strike curbs, signs, or vehicles.

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With multiple trailers, offtracking increases with each additional unit; a triple combination can cut several feet inside the tractor's path in a tight turn.

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Swing wide before a turn, but not so wide that the rear trailer swings into the adjacent lane; check both mirrors and the rear trailer's position before turning.

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Make turns slowly and smoothly; a sharp turn at speed causes the rear trailer to swing out and can cause a rollover or a trailer to tip.

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Use the mirrors continuously during a turn, watching the rear trailer's wheels and the space between the trailer and the curb or the lane line.

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On curves, slow down before entering and maintain a steady speed through the curve; braking or accelerating in the curve can cause the rear trailer to swing or the combination to roll.

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The pivot point of a multiple-trailer combination is the tractor's rear axle, but the rear trailer pivots around the dolly, so the last trailer's path is the hardest to predict.

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When turning right, check the right mirror and the right side of the rear trailer; the rear trailer can clip a curb or a parked car even if the tractor clears it.

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When turning left, watch the left mirror and the rear trailer's swing; the rear trailer can swing into oncoming traffic if the turn is too sharp.

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Allow extra space when changing lanes or merging; the combination is long and the rear trailer may still be in the original lane when the tractor is in the new one.

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Backing a multiple-trailer combination is generally not permitted or is extremely difficult; plan the route so backing is not required.

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If a turn requires backing, get out and check the area, use a spotter, and back slowly; the rear trailer's path is not visible from the cab.

Rearward amplification: in a multiple-trailer combination, a steering input at the tractor is amplified at the rear trailer, so a small movement at the front can cause a large swing at the back.

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Rearward amplification increases with speed and with the number of trailers; a triple combination amplifies more than a double, so reduce speed in curves and lane changes.

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Trailer sway is caused by speed, crosswinds, uneven loading, and sudden steering; if sway starts, ease off the accelerator and steer gently, do not brake hard or steer sharply.

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Rollover risk increases with a high center of gravity and with speed in a curve; slow down before the curve and keep the load low and centered.

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Load the heaviest cargo over or near the trailer axles and keep the load balanced side to side; an off-center load increases sway and rollover risk.

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Check that the load is secured and that the trailer's weight is within the axle and gross limits; an overloaded or unbalanced trailer is harder to control.

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In crosswinds, reduce speed and keep a firm, steady grip on the wheel; a sudden correction can start a sway that amplifies at the rear trailer.

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Avoid sudden lane changes at highway speed with multiple trailers; a quick lane change can cause the rear trailer to swing into the adjacent lane.

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If the rear trailer starts to sway, do not countersteer sharply; ease off the throttle and let the combination straighten, then correct gently.

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Check tire pressure and condition on every trailer; a soft or damaged tire increases sway and can cause a blowout that leads to a rollover.

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Use a lower gear and engine braking on downgrades to control speed without hard braking, which can cause the rear trailer to swing.

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When passing, allow extra time and space; the combination is long and a sudden return to the lane can cause the rear trailer to sway.