CLP - Commercial Learner's Permit Combination Vehicle Operations Questions and Answers

Question 1

When driving a combination vehicle, the 'crack-the-whip' effect is a significant danger. Which of the following is most likely to cause the rear trailer to roll over?

Accepted Answer

Making a sudden or quick lane change.

Answer

The 'crack-the-whip' effect, also known as rearward amplification, happens when a driver makes a quick steering movement, like a sudden lane change. This causes the rear-most trailer to swing out with greater force, which can lead to a rollover, even if the tractor remains stable.

Question 2

You are coupling a tractor to a semitrailer. Before you back under the trailer, the trailer is at the correct height when:

Accepted Answer

The trailer will be raised slightly when the tractor backs under it.

Answer

The trailer should be just low enough that the tractor's fifth wheel will slide under and lift the front of the trailer slightly. If the trailer is too low, the tractor may strike the kingpin incorrectly. If it is too high, it may not couple correctly and could damage the landing gear or fifth wheel.

Question 3

A driver is operating a tractor without a trailer attached, a practice known as 'bobtailing'. Compared to a fully loaded tractor-trailer, how does a bobtail tractor's stopping distance change?

Accepted Answer

It can be longer because there is less weight on the drive axles for traction.

Answer

It is a common misconception that a lighter bobtail tractor stops faster. In reality, it can take longer to stop than a fully loaded unit. The braking system is designed for a heavy load, and without the trailer's weight providing traction on the rear axles, the wheels can lock up easily, causing a skid and increasing the stopping distance.

Question 4

What is the primary, approved use of the trailer hand valve (also known as the trolley valve or Johnson bar)?

Accepted Answer

To test the trailer service brakes.

Answer

The trailer hand valve should only be used to test the application of the trailer's service brakes to ensure they are working correctly. It should not be used for parking, as air could leak out, or for braking during driving, as it can cause the trailer wheels to lock up and skid.

Question 5

When a combination vehicle turns a corner, the rear wheels of the last trailer follow a different path than the front wheels of the tractor. This is called:

Accepted Answer

Off-tracking

Answer

Off-tracking, or 'cheating,' is the term used to describe how the rear wheels of a vehicle or combination vehicle follow a path inside the path of the front wheels when turning. The longer the vehicle, the greater the amount of off-tracking.

(CLP) Commercial Learner's Permit Practice Test

(CLP) Commercial Learner's Permit Practice Test

CLP - Commercial Learner's Permit Combination Vehicle Operations Questions and Answers