California CDL Doubles and Triples Endorsement Test flashcards
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- Converter dolly
- A separate vehicle with a fifth wheel, axle, and brakes that connects a lead trailer to a rear trailer in doubles/triples configurations.
- Offtracking
- The difference between the path of the front wheels and the rear wheels; with multiple trailers, the rear trailer cuts corners more sharply.
- Crack-the-whip effect
- The amplified swaying of the rear trailer in a multiple-trailer combination, especially during sudden maneuvers or lane changes.
- Pintle hook
- A coupling device on the lead trailer or dolly that connects to the lunette eye of the towed trailer; must be latched and secured.
- Safety chains
- Chains that connect the trailer to the towing vehicle as a backup in case the coupling fails; they must be crossed and have proper slack.
- Glad hands
- Couplers for the air lines between the tractor and trailer; the emergency line is red and the service line is blue.
- Fifth wheel jaws
- The locking mechanism on the fifth wheel that grips the trailer kingpin; must be closed and locked after coupling.
- Tug test
- After coupling, pulling forward gently to ensure the fifth wheel jaws are locked and the trailer is secure.
- Landing gear
- The support legs on a trailer or dolly that hold it level when not connected to a tractor; must be fully raised before moving.
- Emergency air line
- The red air line that supplies air to the trailer’s emergency brakes; if disconnected, the trailer brakes apply automatically.
- Service air line
- The blue air line that controls the trailer’s service brakes; it is connected after the emergency line.
- Trailer hand valve
- A valve in the cab that applies only the trailer brakes; used for testing, not for normal braking.
- Spring brakes
- Emergency brakes that apply automatically when air pressure drops below a safe level (around 45 psi).
- Jackknife
- A skid where the tractor and trailer fold at the coupling; corrected by releasing brakes and steering in the desired direction.
- Buttonhook turn
- A turning technique where you pull forward and slightly left before turning right to create more space for the rear trailer.
- Following distance rule
- Allow at least one second per 10 feet of vehicle length; for a 100-foot combination, maintain a 10-second following distance.
- Tiedown working load limit
- The maximum load a tiedown can safely hold; the sum of all tiedowns’ WLL must be at least 50% of the cargo weight.
- Aggregate WLL
- The total working load limit of all tiedowns used to secure a load; must be at least half the weight of the cargo.
- Load distribution
- Evenly spreading weight across axles and trailers; the front trailer should carry the heavier load for stability.
- Cargo securement check
- Inspecting the load and tiedowns after the first 50 miles and every 150 miles or 3 hours thereafter.
- Doubles/triples endorsement
- The T endorsement on a Class A CDL that allows driving a combination of two or three trailers.
- Maximum trailer length
- In most states, each trailer in a doubles/triples combination is limited to 28 feet in length.
- Maximum gross weight
- The total weight of the vehicle and load; for doubles/triples, it is typically 80,000 pounds unless a permit allows more.
- Pre-trip inspection
- A thorough check of the vehicle before each trip, including coupling, brakes, lights, tires, and safety chains.
- Dolly safety chains
- Chains that attach the dolly to the lead trailer; they must be crossed and have enough slack to allow turning.
- Dolly air lines
- Air lines that connect the dolly to the lead trailer and the rear trailer; they must be properly connected and free of leaks.
- Trailer sway
- Side-to-side movement of the trailer; in doubles/triples, it is amplified and corrected by releasing the accelerator and steering straight.
- Crosswinds
- Strong winds from the side that can push the rear trailer; reduce speed and increase following distance to maintain control.
- Engine braking
- Using a lower gear to slow the vehicle on downgrades; helps prevent brake fade and maintains control.
- Brake fade
- Loss of braking power due to overheating; prevented by using engine braking and intermittent braking on long grades.
- Tire blowout procedure
- Hold the steering wheel firmly, maintain speed briefly, steer straight, and slow gradually; avoid hard braking.
- Load shift
- Movement of cargo during transit; reduce speed gradually and pull off the road to secure the load.