Combination Vehicle Operations Flashcards

When making a right turn in a tractor-trailer, you should:

Answer: Drive straight ahead until clear, then swing wide as you complete the turn

Go straight ahead until the rear clears the corner and swing wide at completion so cars can't slip in on your right.

What is 'offtracking'?

Answer: Rear wheels following a different path than front wheels in a turn

Offtracking is when the rear wheels of a long vehicle follow a shorter path than the front wheels during turns.

In a set of doubles, where should the heavier trailer be placed?

Answer: First, directly behind the tractor

The heaviest trailer should be in the first position, right behind the tractor.

When pulling doubles, how should the shut-off valves (cut-out cocks) be set?

Answer: Open on front trailers, closed at the rear of the last trailer

Rear valves on front trailers must be open so air passes through, while those on the last trailer are closed.

How can you verify air has reached the last trailer of a set of doubles?

Answer: Open the emergency line shut-off at the rear of the last trailer and listen for air

Briefly opening the emergency line valve at the rear of the last trailer and hearing air confirms the lines are open.

For a combination vehicle with the engine off and brakes released, what is the maximum acceptable air leakage rate?

Answer: Less than 3 psi per minute

With brakes released, combination vehicles should lose less than 3 psi in one minute.

Why can low-clearance (low-slung) combination units be dangerous at railroad crossings?

Answer: They can get hung up on raised crossings

Low-slung units can get stuck on raised railroad crossings, so check clearance before crossing.