50 questions · 60 min · 80% to pass
Question 1
What position must the converter dolly fifth wheel be in before backing under a trailer?
Answer: Unlocked and open
Question 2
Why chock wheels on all trailers of a triple on a grade?
Answer: Prevent cascade rolling if brakes fail
Question 3
How should a driver inspect the air lines between trailers during a pre-trip inspection of a doubles combination?
Answer: The driver should visually trace each air line from the glad hands at one trailer to the glad hands at the next, checking for kinks, cracks, worn spots, or chafing against metal edges. The lines should be secured so they won't drag on the road or snag on any moving part during operation.
Question 4
Which trailer in a doubles combination creates the greatest off-tracking hazard during right turns, and where is the danger concentrated?
Answer: The rear trailer creates the greatest off-tracking hazard because its axles follow the shortest path through the turn. The danger is concentrated at the rear trailer's axle group, which can run over curbs, strike signs, or hit pedestrians standing near the inside edge of the turning lane.
Question 5
What must be done before a driver walks away from a parked doubles or triples combination to ensure it will not roll?
Answer: The driver must apply the parking brakes on the tractor, set all trailer spring brakes by pulling the trailer air supply control, chock the wheels if on any slope, and verify that the combination is in a stable position. The driver should also confirm that all fifth wheel connections and pintle hooks remain secure while the vehicle is unattended.
Question 6
What happens to the converter dolly axle load when the rear trailer in a doubles combination is loaded significantly heavier than design recommendations?
Answer: An excessively heavy rear trailer increases the tongue weight on the converter dolly's fifth wheel beyond the dolly's rated capacity, which can overload the dolly axle and cause premature tire failure, axle damage, or coupling failure. It also places excessive stress on the lead trailer's rear drawbar and the connection hardware.
Question 7
What is brake lag and how does it specifically affect stopping in a triple combination?
Answer: Brake lag is the delay between when the driver presses the brake pedal and when full braking force is applied at the rear axles. In a triple combination, the brake signal must travel through more air lines and connections to reach the third trailer, meaning the rear trailer may have significantly delayed brake application compared to the tractor, increasing stopping distance.
Question 8
How should a driver turn at intersections with a triple combination?
Answer: Swing wider before turning
Question 9
What happens if the rear trailer is much heavier than the front trailer?
Answer: Increased jackknife or swing risk
Question 10
At what speed range does rearward amplification become most dangerous in double and triple trailer combinations?
Answer: Rearward amplification becomes most dangerous during sudden lane changes or evasive swerves at highway speeds, typically above 55 mph. At these speeds, even a small steering input can cause the rear trailer to sway violently, and the driver may not feel the rear trailer's extreme movement because the tractor remains relatively stable.