NJ CDL Doubles/Triples cheat sheet

Coupling sequence for doubles: secure the rear trailer, back the dolly under the rear trailer's front kingpin, lock the jaws, connect the air lines and electrical cord, then back the tractor's fifth wheel under the lead trailer's kingpin.

The converter dolly carries its own kingpin at the rear; that kingpin must be locked into the rear trailer's front fifth-wheel plate before the dolly is pulled forward.

Always chock the rear trailer wheels before coupling or uncoupling so the trailer cannot roll while the dolly is being handled.

Uncouple in reverse order: release the tractor fifth wheel from the lead trailer, lower the lead trailer landing gear, disconnect lines, pull forward, then separate the dolly from the rear trailer.

The trailer protection valve (emergency relay valve) on each trailer must be closed before disconnecting air lines so the spring brakes stay applied on the separated trailer.

After coupling, tug-test the tractor against the lead trailer with the trailer brakes set to confirm the fifth-wheel jaws are locked.

Verify the dolly's safety chains or locking pin and the gladhand seals after every coupling; a leaking seal at the dolly is a common cause of trailer brake failure.

Never couple or uncouple on a curve, slope, or soft shoulder; the dolly must be in line with the trailer kingpin for the jaws to lock fully.

Inspect the dolly frame for cracks, the kingpin for wear, the fifth-wheel jaws for slack, and the pintle hook or drawbar for deformation before each trip.

Check dolly tires for inflation, tread depth, and matching size; mismatched dolly tires cause the dolly to track poorly and can trigger sway.

Confirm the dolly's air tank, relay valve, and gladhands are secure and leak-free; the dolly supplies brake air to the rear trailer.

Test the rear trailer's brakes independently with the tractor brake applied and the dolly line charged; a dead rear trailer is a serious violation.

Inspect the second trailer's landing gear, mud flaps, lights, and rear-end protection; the rear trailer's lights must be visible from behind the combination.

Check the rear trailer's kingpin plate for cracks and the upper coupler area for rust jacking; a cracked plate can drop the trailer onto the dolly.

Verify all electrical connections at the dolly and rear trailer; a loose cord can chafe and short, killing the rear trailer's lights.

Check the dolly's locking pin and the rear trailer's kingpin locking jaws by pulling forward under brake application after coupling.

Stopping distance for a loaded doubles or triples combination is substantially longer than for a single trailer; increase following distance to at least one second per 10 feet of vehicle length at speeds above 40 mph.

Brake smoothly and progressively; sudden hard braking causes the rear trailer to push the lead trailer and can jackknife the dolly.

The rear trailer's brakes must be synchronized with the lead trailer; if the rear trailer brakes lag, the dolly can be pushed sideways during a stop.

Use engine braking and downshifting on downgrades to avoid overheating the trailer brakes; brake fade on a multi-trailer combination is dangerous.

When stopping, apply the brakes gradually and keep the combination straight; a combination stopped on a curve is harder to restart without dolly damage.

Check the low-air warning and brake application on all trailers before descending a grade; a dead rear trailer brake system means the combination cannot stop safely.

Stab braking (hard application to a stop) is not appropriate for multi-trailer combinations; it increases the risk of trailer swing and dolly jackknife.

After any hard stop, inspect the dolly and rear trailer couplings for damage before resuming.

Offtracking is the difference between the path of the front wheels and the path of the rear wheels; it increases with each additional trailer and with sharper turns.

A triples combination offtracks more than doubles; swing wide at intersections and check mirrors for the rear trailer before completing a turn.

The rear trailer cuts the corner more sharply than the lead trailer; a turn that clears the lead trailer may still clip a curb with the rear trailer.

Use the outside lane for right turns and the inside lane for left turns, and keep the combination straight before entering the turn.

Check both mirrors and the rear trailer's position before changing lanes; the rear trailer can be in a blind spot that the tractor mirrors do not cover.

Maintain lane position by centering the tractor in the lane and monitoring the rear trailer in the mirrors; the rear trailer may drift toward the lane edge.

At intersections, pull forward until the tractor clears the crosswalk before turning so the rear trailer follows the tractor's path.

Offtracking is greatest at low speed and sharp angles; make wide, sweeping turns and avoid tight U-turns with multiple trailers.

Backing a doubles or triples combination is discouraged; if backing is unavoidable, back only in a straight line and use a spotter.

When backing, the rear trailer reacts opposite to the tractor's steering; turn the wheel toward the direction you want the rear trailer to go.

Never back a combination with the dolly at an angle; the dolly can jackknife and damage the kingpin or fifth-wheel jaws.

Park on level ground with the trailer brakes set, wheels chocked, and the combination straight to reduce stress on the dolly.

Use the tractor's mirrors and a spotter to monitor the rear trailer's position while maneuvering in tight spaces.

Before backing, get out and check the area behind the rear trailer for obstacles, pedestrians, and clearance.

Avoid backing onto a slope or soft shoulder; the dolly can shift and the rear trailer can roll.

When parking, set the parking brakes on all trailers and chock the wheels; a combination left on a grade can roll if the brakes release.

Sway is amplified by each additional trailer; a small oscillation in the lead trailer can grow into a fishtail in the rear trailer.

Reduce speed before curves, downgrades, and crosswinds; sway increases with speed and is hardest to control at high speed.

If sway begins, ease off the accelerator and steer smoothly; do not brake hard, which can worsen the oscillation.

Load the trailers so weight is distributed evenly and the rear trailer is not lighter than the lead trailer; a light rear trailer fishtails more easily.

Crosswinds and passing trucks create aerodynamic forces that push the rear trailer; anticipate and reduce speed when passing or being passed.

Keep the combination straight and avoid sudden steering inputs; smooth inputs reduce the chance of inducing sway.

Check tire pressure and suspension on all trailers; a soft tire or worn shock can trigger sway.

If sway persists, pull over safely, inspect the load and tires, and redistribute weight before continuing.

The maximum gross vehicle weight rating is set by the tractor and each trailer's axle ratings; never exceed the lowest-rated component.

The steer axle, drive axles, and each trailer axle have individual weight limits; distribute load so no axle is overloaded.

The rear trailer must carry enough weight to keep its tires firmly on the road; too little weight causes fishtailing.

Load securement must meet the Federal Motor Carrier Safety Administration's cargo securement rules; use adequate tie-downs and check them after the first few miles.

The kingpin load on the dolly and the fifth-wheel load on the tractor must stay within the rated capacity of the coupling.

Check axle weights at a scale before departure; a combination that is legal on the tractor may be overweight on the rear trailer axle.

Distribute weight evenly side to side; an unbalanced load increases sway and tire wear.

Never exceed the tire load rating; overloading a tire can cause a blowout that leads to loss of control.

Doubles and triples may not be operated on certain roads; check state and local restrictions before routing a combination.

A commercial driver's license with the doubles/triples endorsement is required to operate a combination of two or three trailers.

Never transport passengers in a trailer; trailers are for cargo only.

Do not tow more than three trailers; triples is the maximum allowed under federal rules.

Never operate a combination with a defective coupling, brake system, or lighting system; out-of-service defects must be corrected before driving.

Do not exceed the posted speed limit or the tire speed rating; a combination is less stable at high speed.

Use warning devices (triangles, flares) when stopped on a roadway; place them at the required distances to warn traffic.

Do not back a combination on a public road unless necessary and safe; backing is a common cause of collisions.