California CDL Doubles and Triples Endorsement Test cheat sheet

Pre-trip inspection of doubles/triples must include the converter dolly: check the dolly frame, pintle hook, safety chains, air lines, and electrical cord.

Check the fifth wheel plate for proper lubrication, secure mounting, and that the jaws are closed and locked around the kingpin.

Inspect the glad hands and air lines for cracks, leaks, or chafing; ensure the couplers are sealed and the lines are properly supported.

Verify that the trailer landing gear is fully raised and the crank handle is secured before moving.

Check all trailer lights (clearance, brake, turn, and marker) and reflectors; use the tractor’s light circuit to test each trailer individually.

Inspect tires for tread depth, sidewall damage, and proper inflation; dual tires must not touch and should have matched circumference.

Test the trailer brakes with the tractor parking brake set: apply the hand valve and listen for brake application at each trailer.

Check the safety chains: they must be crossed under the dolly tongue and have enough slack to allow turning but not drag on the ground.

Inspect the dolly’s pintle hook for wear and ensure the latch is closed and secured with a safety pin.

When coupling a dolly to a trailer, back under the trailer until the fifth wheel jaws lock, then tug test by pulling forward gently.

Connect the emergency air line (red) first, then the service line (blue), to prevent trailer movement if the lines are crossed.

After coupling, check that the trailer apron is resting on the fifth wheel and the jaws are locked; visually inspect the locking jaws.

Uncoupling: set the trailer parking brakes, lower the landing gear, disconnect the air lines (service first, then emergency), and release the fifth wheel.

When uncoupling a dolly, place the dolly landing gear (or support legs) on firm ground and ensure the dolly is stable before releasing the pintle hook.

Always use the trailer hand valve to test that the trailer brakes hold before uncoupling; never rely solely on the tractor parking brake.

Coupling sequence for doubles: connect the rear trailer to the dolly first, then the dolly to the front trailer, then the front trailer to the tractor.

After coupling, check that the safety chains are crossed and attached, the air lines are not tangled, and the electrical cord is plugged in.

With multiple trailers, the rear trailer tends to swing out (offtrack) more during turns; allow extra room and swing wide.

The rear trailer amplifies sway; if sway starts, release the accelerator and steer straight-do not brake hard or countersteer abruptly.

When backing, doubles and triples are generally not backed except in a straight line for a short distance; plan ahead to avoid backing.

The converter dolly must be inspected for proper coupling and safety chains before each trip; a loose dolly can cause jackknifing.

When driving over railroad tracks or rough surfaces, reduce speed to prevent the trailers from bouncing and the dolly from becoming airborne.

In strong crosswinds, the rear trailer acts as a sail; reduce speed and increase following distance to maintain control.

The “crack-the-whip” effect is greatest at the rear trailer; make lane changes and turns smoothly and gradually.

When descending a grade, use a lower gear and engine braking; the rear trailer can push the tractor if brakes are applied too hard.

A converter dolly is a separate vehicle with its own fifth wheel, axle, and brakes; it must be coupled securely to the lead trailer and the rear trailer.

The dolly’s air lines must be connected to the lead trailer’s emergency and service lines; the rear trailer’s lines connect to the dolly.

The dolly’s safety chains must be crossed and attached to the lead trailer’s frame; the rear trailer’s chains attach to the dolly.

Check the dolly’s pintle hook and lunette eye for wear; the latch must be closed and secured with a safety pin.

The dolly’s brakes must be operational and synchronized with the trailer brakes; test them during the pre-trip inspection.

When turning, the dolly’s wheels track inside the path of the lead trailer, increasing offtracking; watch the dolly in the mirrors.

Never move a dolly without a trailer attached unless it is properly supported and the pintle hook is secured.

The dolly’s electrical cord must be plugged into the lead trailer to provide power to the rear trailer’s lights.

The total stopping distance for doubles/triples is longer than for a single trailer; increase following distance to at least one second per 10 feet of vehicle length.

Use the trailer hand valve only to test trailer brakes; never use it for normal braking because it can cause the trailer to skid.

Brake smoothly and progressively; sudden braking can cause the rear trailer to jackknife or swing out.

When braking on a curve, reduce speed before entering the curve and avoid braking while turning if possible.

The emergency (spring) brakes on trailers apply automatically if air pressure drops below 45 psi; monitor the air gauge.

In a brake emergency, downshift and use engine braking; if the brakes fail, pump the brake pedal to build pressure.

After driving through water, test the brakes gently to dry them; wet brakes may pull or grab unevenly.

When descending a long grade, use a lower gear and intermittent braking; continuous braking can overheat the brakes and cause fade.

If the rear trailer starts to skid, release the brakes and steer in the direction of the skid; do not countersteer abruptly.

To correct a jackknife, release the brakes, steer the tractor in the direction you want to go, and accelerate gently to pull the trailer straight.

If a tire blows out, hold the steering wheel firmly, maintain speed briefly, and steer straight while slowing gradually.

In a skid, look and steer where you want to go; avoid overcorrecting, which can cause a secondary skid.

If the trailer brakes fail, use the tractor brakes and engine braking; if the tractor brakes fail, use the trailer hand valve to stop.

If the load shifts, reduce speed gradually and pull off the road; avoid sudden maneuvers that could worsen the shift.

When an emergency stop is necessary, brake firmly and steer to a safe location; do not lock the wheels.

After any emergency maneuver, check the vehicles and load for damage before continuing.

Offtracking is the difference between the path of the front wheels and the rear wheels; with multiple trailers, the rear trailer cuts the corner more sharply.

When turning right, swing wide to the left to keep the rear trailer from hitting the curb or objects; watch the rear trailer in the mirrors.

When turning left, be careful not to swing into oncoming traffic; allow extra room for the rear trailer to clear.

The longer the combination, the more the rear trailer off tracks; in a tight turn, the rear trailer may cross into adjacent lanes.

Use the “buttonhook” turn technique: pull forward and slightly left before turning right to create more space.

When negotiating a curve, reduce speed before entering and maintain a steady speed; braking in a curve can cause a skid.

Check mirrors frequently during turns to monitor the rear trailer and dolly; use a spotter if available.

On narrow roads, keep the rear trailer from dropping off the pavement; if it does, slow down and steer gently back onto the road.

The safe following distance for doubles/triples is at least one second per 10 feet of total vehicle length; for a 100-foot combination, that is 10 seconds.

Increase following distance in bad weather, at night, or when the road is wet or icy; doubles/triples need more space to stop.

Maintain a speed that allows you to stop within the distance you can see ahead; never overdrive your headlights.

When passing, allow extra time and distance; the rear trailer may sway or off track, so ensure you have enough clear space.

Avoid sudden lane changes; signal early and move smoothly to prevent trailer sway.

In traffic, leave room ahead to allow for smooth braking and to avoid abrupt stops that can cause a rear-end collision.

When being passed, maintain a steady speed and keep to the right; do not speed up.

On downgrades, control speed with engine braking and a lower gear; do not rely solely on the brakes.

A doubles/triples endorsement (T) is required to drive a combination of two or three trailers; it is added to a Class A CDL.

The maximum length for doubles is 28 feet per trailer; triples are typically limited to 28-foot trailers as well, but check state laws.

The maximum gross vehicle weight for doubles/triples is 80,000 pounds unless a permit allows more.

Safety chains are required on the dolly and must be strong enough to hold the trailer if the coupling fails.

The converter dolly must have its own brakes and lights; it is considered a separate vehicle for inspection purposes.

When operating doubles/triples, you must obey all traffic laws and weight restrictions; some states have specific routes for these combinations.

A pre-trip inspection is required before each trip; check coupling, brakes, lights, tires, and safety chains.

The vehicle must have a fire extinguisher, warning triangles, and spare fuses; check that they are present and in working order.

Cargo must be secured with tiedowns that meet the working load limit (WLL) requirements; the aggregate WLL must be at least 50% of the cargo weight.

For loads over 10,000 pounds, use at least four tiedowns; for loads under 10,000 pounds, use at least two.

Distribute weight evenly across the axles; check that the load does not exceed the tire load rating or axle weight limits.

The load must not block the driver’s view or interfere with the safe operation of the vehicle.

Secure cargo to prevent shifting; use blocking, bracing, or dunnage to fill gaps.

Check the load and tiedowns after the first 50 miles and every 150 miles or 3 hours thereafter.

The front trailer should carry the heavier load to improve stability; never overload the rear trailer.

All cargo must be covered if it could blow off or spill; use a tarp or other cover.