CDL Doubles Triples Practice Test 1

Question 1

What is rearward amplification?

Accepted Answer

'Crack-the-whip' effect when making quick lane changes

Answer

Rearward amplification, also known as the 'crack-the-whip' effect, describes how quick steering movements can be amplified down a set of multiple trailers. The last trailer in a double or triple combination will swing out much wider and with greater force than the tractor. This effect makes quick lane changes or sudden maneuvers extremely dangerous with multiple trailers.

Question 2

In a set of triples, where should the heaviest trailer be?

Accepted Answer

First trailer position (behind the tractor)

Answer

In a set of triples, the heaviest trailer should always be placed in the first position, directly behind the tractor. This configuration provides the most stability and reduces the effects of rearward amplification. Placing lighter trailers further back helps maintain control and minimizes the 'crack-the-whip' effect.

Question 3

Why should you never disconnect the pintle hook with the dolly still under the rear trailer?

Accepted Answer

The dolly tow bar may fly up, possibly causing injury

Answer

Never disconnect the pintle hook with the dolly still under the rear trailer because the dolly tow bar may fly up violently. The tow bar is under tension and can spring upwards with considerable force, potentially causing serious injury to anyone nearby. Always ensure the dolly is properly supported or disconnected from the trailer before uncoupling the pintle hook.

Question 4

When connecting the converter dolly to the front trailer, what do you do first?

Accepted Answer

Back first semitrailer in front of dolly tongue

Answer

When connecting the converter dolly to the front trailer, the first step is to back the first semitrailer in front of the dolly tongue. This positions the trailer correctly for coupling. Once the trailer is aligned, you can then proceed with connecting the pintle hook and air lines.

Question 5

If a second trailer does not have spring brakes, how should you set the brakes when you are coupling?

Accepted Answer

Drive the tractor close to the trailer, connect the emergency line to charge the trailer air tank and disconnect the emergency line

Answer

If a second trailer does not have spring brakes, you must manually set its brakes for coupling. This is done by connecting the emergency line to charge the trailer's air tank, then disconnecting the emergency line. This will cause the trailer's service brakes to apply and hold, as they rely on air pressure to release, not apply.

CDL Practice Test

CDL Practice Test

CDL Doubles Triples Practice Test 1