Commercial Driving Combination Vehicles 2

Question 1

At what angle should you position the tractor when backing a semi-trailer into a tight dock?

Accepted Answer

At a 45-degree angle to begin the back

Answer

Starting the backing maneuver at approximately a 45-degree angle to the dock allows the driver to steer the trailer into the bay with controlled corrections.

Question 2

What is the converter dolly used for in a doubles or triples combination?

Accepted Answer

It converts a semi-trailer into a full trailer by providing a set of axles and a fifth wheel

Answer

A converter dolly attaches to the rear of a lead trailer and provides a fifth wheel for coupling the next trailer, effectively converting a semi-trailer into a full trailer.

Question 3

When driving a combination vehicle, how does the off-tracking of a long trailer affect turning?

Accepted Answer

The rear wheels cut inside the path of the front wheels, requiring a wider turn

Answer

Off-tracking causes the rear trailer wheels to follow a shorter, inside arc compared to the front tractor wheels, requiring drivers to swing wider to keep all wheels in the lane.

Question 4

What is the maximum number of trailers that can be towed in a triples combination under federal regulations?

Accepted Answer

3 trailers

Answer

Federal regulations permit a maximum of three trailers (triples) in a combination vehicle, and even this is restricted to certain states.

Question 5

When should the tractor protection valve close automatically?

Accepted Answer

When air pressure in the tractor drops to approximately 20–45 psi

Answer

The tractor protection valve closes automatically when tractor air pressure drops to roughly 20–45 psi, sealing off the trailer to prevent the tractor's air supply from being fully depleted.

Commercial Driving Practice Test

Commercial Driving Practice Test

Commercial Driving Combination Vehicles 2