Combination Vehicle Operations Flashcards

Which trailer should be placed immediately behind the tractor in a double trailer combination?

Answer: The heavier trailer, to improve stability and reduce rearward amplification

Placing the heavier trailer closest to the tractor reduces rearward amplification and improves overall stability of the combination.

What should you do if you discover during a pre-trip that one glad hand seal is cracked or missing?

Answer: Replace the seal before driving because air leaks can cause brake failure

A faulty glad hand seal will cause air loss, which can reduce or eliminate trailer braking force, making the vehicle unsafe to operate.

When backing a combination vehicle, how does the trailer respond when you turn the steering wheel left?

Answer: The trailer moves to the right

When backing, turning left causes the trailer to move to the right because the pivot point reverses the direction of trailer travel.

What is the maximum length of a safety chain or cable used to secure a converter dolly to the lead trailer?

Answer: Long enough to prevent the dolly from swinging wide but short enough to keep it under the trailer if the pintle hook fails

Safety chains must be short enough to prevent the dolly from touching the ground if it separates, limiting swing and ground contact.

What is the proper way to inspect the coupling after backing under a trailer?

Answer: Pull gently forward against the trailer brakes and look underneath to confirm the fifth wheel jaws are locked around the kingpin

A forward tug against locked trailer brakes plus a visual inspection underneath confirms the fifth wheel jaws have fully engaged the kingpin.

Which air line on a combination vehicle is colored BLUE?

Answer: The service brake line

The service line (which carries brake application pressure) is coded blue, while the emergency/supply line is coded red.

What happens to handling when a combination vehicle travels too fast around a curve?

Answer: The trailer may roll over first because its center of gravity is higher than the tractor's

Trailers have a higher center of gravity and can tip in a curve even when the tractor remains upright, making trailer rollover a leading concern.