NJ CDL Doubles/Triples flashcards
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- Converter dolly
- A small axle assembly with a fifth-wheel plate and a kingpin that connects the lead trailer to the rear trailer in a doubles or triples combination.
- Coupling order for doubles
- Secure the rear trailer, back the dolly under its kingpin, lock the jaws, connect lines, then back the tractor under the lead trailer's kingpin.
- Uncoupling order
- Release the tractor from the lead trailer, lower the landing gear, disconnect lines, pull forward, then separate the dolly from the rear trailer.
- Tug test
- After coupling, pull gently against the trailer with the trailer brakes set to confirm the fifth-wheel jaws are locked and will not release.
- Trailer protection valve
- A valve that keeps the spring brakes applied on a separated trailer when the air lines are disconnected, preventing the trailer from rolling.
- Dolly inspection points
- Check the dolly frame for cracks, the kingpin for wear, the fifth-wheel jaws for slack, and the pintle hook or drawbar for deformation.
- Rear trailer brake test
- With the tractor brake applied and the dolly line charged, confirm the rear trailer's brakes apply; a dead rear trailer is a serious violation.
- Rear trailer kingpin plate
- The upper coupler area of the rear trailer; inspect for cracks and rust jacking because a cracked plate can drop the trailer onto the dolly.
- Following distance for doubles
- Increase following distance to at least one second per 10 feet of vehicle length at speeds above 40 mph because stopping distance is longer.
- Brake lag on rear trailer
- If the rear trailer's brakes apply later than the lead trailer's, the dolly can be pushed sideways during a stop, risking jackknife.
- Engine braking on downgrades
- Use engine braking and downshifting on long downgrades to avoid overheating trailer brakes and losing braking power to fade.
- Brake inspection before downgrade
- Check the low-air warning and confirm all trailers' brakes apply before descending a grade; a dead rear trailer means the combination cannot stop safely.
- Offtracking
- 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.
- Triples offtracking
- A triples combination offtracks more than doubles; swing wide at intersections and check mirrors for the rear trailer before completing a turn.
- Rear trailer corner cut
- The rear trailer cuts a corner more sharply than the lead trailer; a turn that clears the lead trailer may still clip a curb with the rear trailer.
- Lane position with doubles
- Center the tractor in the lane and monitor the rear trailer in the mirrors; the rear trailer may drift toward the lane edge.
- Backing a combination
- Backing doubles or triples is discouraged; if unavoidable, back only in a straight line with a spotter and never with the dolly at an angle.
- Rear trailer steering response
- 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.
- Parking a combination
- Park on level ground with trailer brakes set, wheels chocked, and the combination straight to reduce stress on the dolly and prevent rolling.
- Spotter use
- Use a spotter and the tractor's mirrors to monitor the rear trailer's position while maneuvering in tight spaces or backing.
- Sway amplification
- Sway is amplified by each additional trailer; a small oscillation in the lead trailer can grow into a fishtail in the rear trailer.
- Sway recovery
- If sway begins, ease off the accelerator and steer smoothly; do not brake hard, which can worsen the oscillation.
- Rear trailer weight and sway
- A rear trailer that is too light fishtails more easily; load trailers so weight is distributed evenly and the rear trailer is not lighter than the lead.
- Crosswind effect
- Crosswinds and passing trucks create aerodynamic forces that push the rear trailer; anticipate and reduce speed when passing or being passed.
- Axle weight limits
- The steer axle, drive axles, and each trailer axle have individual weight limits; distribute load so no axle is overloaded.
- Gross vehicle weight rating
- The maximum gross vehicle weight rating is set by the tractor and each trailer's axle ratings; never exceed the lowest-rated component.
- Cargo securement rules
- Load securement must meet FMCSA cargo securement rules; use adequate tie-downs and check them after the first few miles.
- Tire load rating
- Never exceed the tire load rating; overloading a tire can cause a blowout that leads to loss of control of the combination.
- Doubles/triples endorsement
- A commercial driver's license with the doubles/triples endorsement is required to operate a combination of two or three trailers.
- Maximum trailer count
- Do not tow more than three trailers; triples is the maximum allowed under federal rules for a doubles/triples combination.
- Route restrictions
- Doubles and triples may not be operated on certain roads; check state and local restrictions before routing a combination.
- Warning devices
- Use warning devices such as triangles or flares when stopped on a roadway; place them at the required distances to warn traffic.