PA CDL Doubles/Triples flashcards
PA CDL Doubles/Triples · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Coupling order for doubles
- Secure the rear trailer first, then the middle trailer, then the tractor to the lead trailer, so no unsecured trailer is left free to roll during the process.
- Tug test after coupling
- Pull gently forward against the locked trailer, then walk back and visually confirm the fifth wheel jaws closed around the kingpin before driving away.
- Chock before uncoupling
- Chock or lock the wheels of any trailer before releasing its spring brakes or disconnecting air lines, since an unchocked trailer can roll on a grade.
- Converter dolly purpose
- A converter dolly provides a fifth wheel and drawbar so a tractor designed for one trailer can tow doubles or triples legally and safely.
- Dolly fifth wheel check
- The dolly fifth wheel must be greased and its jaws fully closed around the kingpin; a partial latch can release under braking or on a bump.
- Dolly safety chains
- Safety chains or a secondary lock back up the primary coupling; a missing or twisted chain is a defect that can put the combination out of service.
- Dolly drawbar latch
- The drawbar attaches to the lead trailer's rear with a pintle-style coupling; confirm the latch is closed and the safety pin is inserted.
- Off-tracking definition
- Off-tracking is how far the rear trailer cuts inside the path of the tractor's front wheels in a turn, increasing with each added trailer.
- Rearward amplification
- In a quick maneuver, the last trailer swings farther sideways than the tractor, so steer smoothly and avoid sudden lane changes or evasive inputs.
- Right turn setup
- Move left within your lane before turning right, then re-check the right mirror to confirm the rear trailer clears the curb and any roadside objects.
- Backing doubles and triples
- A full doubles or triples combination is unstable in reverse; back one unit at a time and avoid backing the entire combination unless absolutely necessary.
- Mirror tracking through turns
- Watch the rear trailer in the mirror through every turn; if you cannot see it, you cannot confirm it cleared the curb, sign, or parked vehicle.
- Progressive brake application
- Apply brakes smoothly and progressively; hard or stab braking can cause the rear trailer to jackknife or swing out of control.
- Trailer hand valve use
- Use the trailer hand valve only to test trailer brakes, never for normal stopping, because it can make the trailer swing and does not brake the tractor.
- Downgrade braking rule
- Select a low gear before descending and use engine braking; continuous service brake use overheats drums and causes brake fade on heavy combinations.
- Low-air warning response
- When the low-air buzzer sounds, trailer spring brakes will apply automatically; slow down and stop safely before the combination loses control.
- Brake test after coupling
- Pull forward slowly and apply the brakes to confirm every trailer is braking, not just the tractor, before committing to the road.
- Walk-around inspection scope
- Inspect every unit: tractor, lead trailer, dolly, and each rear trailer, because a defect on any one unit affects the whole combination.
- Air line inspection
- Check all air lines and electrical cords for chafing, cracks, and secure connections; a disconnected line means no trailer brakes or no lights.
- Light check on all trailers
- Confirm clearance, marker, brake, turn, and plate lamps work on every trailer; a burned-out rear light hides the whole combination from traffic.
- Dolly tire check
- Inspect the dolly tires for condition and inflation; a soft dolly tire can cause sway and poor tracking of the trailers behind it.
- Following distance rule
- Allow at least one second per 10 feet of combination length, plus extra for speed and load; doubles and triples need far more than a single trailer.
- Sway correction technique
- If the rear trailer starts to sway, ease off the accelerator rather than braking hard; hard braking can worsen the sway and cause a jackknife.
- Crosswind handling
- In strong crosswinds, slow down and grip the wheel firmly; the rear trailer acts like a sail and can push the whole combination sideways.
- Space cushion need
- Maintain a cushion on all sides; a rear trailer cannot stop or swerve as quickly as a car, so leave escape room ahead and beside you.
- Axle weight limit rule
- Gross combination weight must not exceed the sum of axle weight ratings; each axle, including the dolly axle, has its own separate limit.
- Load placement for doubles
- Load the lead trailer heavier than the rear trailers where possible; a light lead trailer with heavy rear trailers causes poor tracking and sway.
- Dolly axle overload cause
- The dolly axle carries weight transferred from the lead trailer's rear; an overloaded dolly axle usually means the load sits too far back.
- Bridge formula limit
- Bridge formula limits tie allowable weight to axle spacing; closely spaced axles cannot legally carry as much weight as widely spaced ones.
- Pennsylvania weight limit
- Pennsylvania's legal maximum gross vehicle weight on interstate highways is 80,000 pounds; state and local roads may post lower limits.
- Pennsylvania width limit
- Maximum width is generally 8 feet 6 inches (102 inches) for standard combinations; anything wider requires an oversize permit from PennDOT.
- Pennsylvania height limit
- Maximum height is generally 13 feet 6 inches (162 inches); check posted clearance signs on your route before departure with a tall combination.