NY CDL Doubles and Triples flashcards

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

Tug test

After coupling, pull forward gently with the trailer brakes set. The tractor should not move. If it moves, the fifth wheel jaws are not locked and you must recouple.

Fifth wheel jaw check

Look at the fifth wheel from the side after coupling. The jaws should be closed around the kingpin, the release lever should be locked, and the safety pin should be in place.

Landing gear before coupling

Raise the landing gear fully after the tractor is under the trailer. Extended gear can catch on the ground or lift the tractor when you pull forward.

Uncoupling order

Set the trailer brakes, lower the landing gear to the ground, release the fifth wheel, then pull forward slowly. Disconnect the air lines and cord before pulling out.

Converter dolly

A dolly with its own fifth wheel and kingpin that connects the first trailer to the second trailer in a doubles or triples combination. It has its own air and electrical connections.

Dolly air line order

Connect the dolly's emergency line to the tractor's emergency line and the dolly's service line to the tractor's service line. Crossed lines cause the trailer brakes to release when you brake.

Dolly pintle hook

The coupling on the dolly that attaches to the first trailer's drawbar. Check it for cracks, wear, and a missing pin; a worn hook can separate under load.

Combination inspection

Check every unit, not just the tractor: each trailer's brakes, lights, tires, and the dolly's connections. A missed connection on the rear trailer is invisible from the cab.

Blue air line

The service or emergency line on a trailer. It carries the air signal that applies the trailer brakes. It must not be crossed with the red supply line.

Red air line

The supply line that feeds air pressure to the trailer. It must connect to the trailer's supply inlet, not the service inlet, or the brakes will not work correctly.

Gladhand leak check

Listen for a steady hiss at the gladhands after connecting. A leak means a bad gasket or a partially engaged coupler and causes slow pressure loss.

Breakaway valve

A valve on the trailer that applies the trailer brakes if the air lines separate from the tractor. It is part of the emergency braking system and must be checked.

Air pressure drop test

With the engine off and brakes released, pressure should not drop more than about 3 psi per minute. A larger drop indicates a leak in the lines or connections.

Following distance formula

Allow at least one second per 10 feet of vehicle length plus one second. A 100-foot combination needs at least 11 seconds in good conditions, more in poor weather.

Trailer hand valve use

Use the trailer hand valve only to test trailer brakes, never to park or hold the vehicle. Using it while moving can cause a jackknife.

Braking with multiple trailers

Brake smoothly and progressively in a straight line. Sudden hard braking causes the rear trailer to push the tractor and can cause a jackknife or trailer swing.

Downgrade gear selection

Select a low gear before starting down a grade and use engine braking. Riding the brakes can cause fade and leave the combination without stopping power.

Jackknife recovery

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

Offtracking

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

Offtracking with triples

Offtracking increases with each additional trailer. A triple combination can cut several feet inside the tractor's path in a tight turn, so swing wider and turn slower.

Right turn mirror check

When turning right, watch 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.

Curve speed control

Slow down before entering a curve and keep a steady speed through it. Braking or accelerating in the curve can cause the rear trailer to swing or the combination to roll.

Pivot point of combination

The tractor pivots at its rear axle, but the rear trailer pivots around the dolly. The last trailer's path is the hardest to predict, so watch it in every turn.

Backing multiple trailers

Backing a doubles or triples combination is generally not permitted or is extremely difficult. Plan the route so backing is not required; if needed, use a spotter.

Rearward amplification

A steering input at the tractor is amplified at the rear trailer. A small movement at the front can cause a large swing at the back, especially at higher speeds.

Speed and amplification

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

Trailer sway correction

If sway starts, ease off the accelerator and steer gently. Do not brake hard or steer sharply, which can amplify the sway and cause a rollover.

Rollover risk factors

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.

Load placement

Place 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.

Crosswind handling

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.

Lane change with multiple trailers

Avoid sudden lane changes at highway speed. A quick lane change can cause the rear trailer to swing into the adjacent lane and strike another vehicle.

Tire pressure and sway

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.