Ohio CDL Doubles and Triples Endorsement Test cheat sheet

Coupling order for a set of doubles: tractor to first (lead) trailer, then converter dolly to rear of lead trailer, then second (rear) trailer to the dolly.

Before backing under a trailer, check that the trailer kingpin and fifth-wheel jaws are aligned and that the trailer floor is at the correct height so the tractor will not strike the trailer nose.

After coupling, do a pull test: apply the trailer brakes, release the tractor parking brake, and gently pull forward; the tractor must not move if the jaws are locked.

Verify the locking jaws closed around the kingpin shank by visual check and tug test; a high hook that rests on top of the fifth wheel will drop the trailer later.

Connect the air lines after the kingpin is locked: emergency (supply) line to emergency gladhand, service line to service gladhand; cross-connection causes trailer brakes to release or stay locked.

Uncoupling order is the reverse of coupling: drop the rear trailer first, then the dolly, then the lead trailer.

When uncoupling, chock the trailer wheels, lower the landing gear to firm ground contact, disconnect air lines and electrical cord, then release the fifth-wheel jaws and pull out slowly.

A converter dolly must be secured so it cannot roll when detached; set its spring brakes or chock its wheels before walking away.

Inspect the whole combination, not just the tractor: every coupling point, every air line, every electrical connection, and every set of trailer brakes must be checked.

Check that the converter dolly is properly attached at both ends and that its safety chains or locking pins are engaged.

Test the trailer service brakes on each trailer separately; a single dead trailer brake circuit can lengthen stopping distance significantly.

Look for air leaks at all gladhands and dolly connections; with the system charged, listen for hissing and watch the gauge for pressure drop.

Confirm the electrical cord is not dragging or chafed and that stop, turn, and clearance lights work on every trailer.

Check tire condition and inflation on all axles, including dolly tires; a failed dolly tire can cause loss of control.

Verify the rear trailer's rear-end protection (bumper) and that reflective tape and lights are intact.

Check that cargo is secured on each trailer and that weight is distributed so no axle is overloaded.

Offtracking increases with each added trailer: the rear trailer cuts a tighter path than the tractor, so swing wide on turns and watch the rear trailer in the mirrors.

On a right turn, the rear trailer of a set of doubles may track inside the curb line; allow extra room and check the right mirror through the turn.

When backing a set of doubles, only the rear trailer responds directly to steering; the lead trailer and dolly react unpredictably, so avoid backing whenever possible.

If backing is unavoidable, back slowly and use a spotter; a slight steering input at the rear trailer can jackknife the dolly quickly.

Lane changes require more time and distance with multiple trailers; signal early and check mirrors for the full length of the combination.

The pivot points (fifth wheel, dolly) mean the combination can 'cheat' or track off-line; keep the combination straight when crossing railroad tracks or narrow bridges.

When turning at an intersection, pull forward until the tractor clears the corner, then turn; cutting the corner drags the rear trailer over the curb.

Following distance should be increased because the combination is longer and heavier; a rule of thumb is at least one second per 10 feet of combination length plus two seconds.

Stopping distance increases with the number of trailers because total weight rises while the tractor's braking effort does not.

Brake application must be smooth and progressive; a hard stab can cause the rear trailer to swing or the combination to jackknife.

Use engine braking and downshifting to control speed on downgrades; continuous service brake use can overheat the tractor brakes.

The trailer hand valve (trolley valve) should not be used for parking or for normal stopping; use it only to test trailer brakes.

With a set of doubles, the rear trailer's brakes do the least work; if the rear trailer brakes are out of adjustment, the combination may push and jackknife.

Check brake adjustment on all trailers before driving; out-of-adjustment brakes are a leading cause of brake failure on long downgrades.

When stopping, allow extra distance and brake earlier; the combination may take significantly farther to stop than a single trailer.

After a hard stop, check that the rear trailer has not swung out of line and that air pressure has recovered before proceeding.

A converter dolly has its own air tank, spring brakes, and a fifth wheel that carries the rear trailer's kingpin.

The dolly's air lines connect to the lead trailer's rear gladhands; the rear trailer's air lines connect to the dolly's gladhands.

Emergency (supply) gladhands are typically on the driver's side and service gladhands on the passenger side; matching color-coded lines helps prevent cross-connection.

Cross-connected air lines can cause the trailer brakes to release when they should apply, or to stay applied and drag.

The dolly's spring brakes set automatically when air pressure is lost, which is why the dolly must be chocked or its brakes set when parked.

Check the dolly's safety chains and locking pins; a dolly that separates from the lead trailer can cause a serious crash.

After connecting all air lines, charge the system and check for leaks at each gladhand; a leaking dolly connection can drain the whole system.

Test that the dolly's brakes apply and release with the tractor's brake pedal before moving.

Trailer sway (fish-tailing) is corrected by releasing the accelerator and steering straight ahead; do not steer into the sway or apply the brakes hard.

If the rear trailer begins to swing, ease off the accelerator and let the combination straighten; hard braking can worsen the swing.

A drive-wheel skid is corrected by releasing the brakes and steering in the direction you want the front of the tractor to go.

A steer-wheel skid is corrected by releasing the brakes and steering in the direction the rear of the tractor is sliding.

If a trailer jackknifes, release the brakes and steer to straighten the combination; do not accelerate out of a jackknife.

In an emergency stop, brake firmly but progressively and keep the steering straight; lockup on any axle reduces control.

If a tire blows on a trailer, hold the steering wheel firmly, ease off the accelerator, and avoid hard braking until the combination slows.

When a dolly or trailer separates, do not chase it; slow down, move to a safe location, and call for help.

Gross combination weight (GCW) is the total weight of the tractor, all trailers, cargo, fuel, and driver; it must not exceed the rated GCW of the tractor.

Each axle has a maximum weight rating, and each trailer has a gross vehicle weight rating (GVWR); no axle or trailer may exceed its rating.

The steer axle, drive axles, dolly axle, and trailer axles each carry a share of the load; shifting cargo changes the distribution.

A trailer loaded too heavily at the rear can lift the tractor's drive axles, reducing traction and braking.

Load the lead trailer heavier than the rear trailer when possible; a light lead trailer with a heavy rear trailer increases sway.

Check weight distribution at a scale before a long trip; axle overloads can cause tire failure and brake problems.

The bridge formula limits the weight that can be carried on a group of axles based on the distance between them.

Cargo must be secured on each trailer independently; a shifting load on one trailer can affect the whole combination.