Washington DC CDL Combination Practice Test (DC) 2

5 out of 5 (33 votes)
80% Passing score
20 Questions
4 Mistakes allowed
Prepare for your DC CDL combination test with our comprehensive DC learners permit practice test. This test features 20 multiple-choice questions designed to cover key areas such as inspection procedures, safe driving practices, air brake systems, and more. By tackling these varied questions, you'll gain the confidence and knowledge needed to excel in the actual permit test. To pass, you need to correctly answer at least 16 questions, ensuring you have a strong grasp of the material. The DMV practice test offers a stress-free environment for learning, unlike the pressure-filled atmosphere of the official DMV written test. This relaxed setting allows you to focus on mastering the essential topics without the added anxiety. Our extensive pool of questions ensures a thorough preparation, giving you a wide range of scenarios and situations to consider. A crucial aspect of the Washington DC CDL combination practice test is understanding the risks associated with jackknifing. This dangerous situation occurs when the trailer swings out of alignment with the tractor, often due to sudden braking or poor handling. By learning to avoid jackknifing through smooth braking and careful handling, you'll be better prepared to drive safely on DC's diverse roadways. Driving in DC presents unique challenges. From navigating the busy streets around the National Mall to handling the winding roads of Rock Creek Park, local drivers must be adept at managing various driving conditions. Our Washington DC DMV knowledge practice test prepares you for these real-world situations, ensuring you can handle the city's traffic with confidence. At the end of each combination CDL practice test, you receive a detailed summary of your performance. This summary highlights the questions you answered incorrectly, along with the correct answers, allowing you to learn from your mistakes and improve your knowledge. This feedback is invaluable in helping you understand the material thoroughly and prepare effectively for the permit test. Whether you're navigating the congested avenues of downtown DC or the quieter suburban streets, our combination CDL test equips you with the skills and knowledge needed for safe driving. Take advantage of this valuable resource to enhance your preparation and ensure you're ready for the DMV permit practice test.
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Sample Washington DC Combination Test Questions

Question 1

The trailer hand valve should be used:

  1. A Together with the foot brake during every stop
  2. B Only when the trailer is fully loaded
  3. C As the primary emergency-braking control
  4. D To test the trailer brakes

Correct answer: D – To test the trailer brakes

The trailer hand valve, also called the trolley valve or Johnson bar, should be used to test the trailer brakes. It should not be used for normal driving because applying only the trailer brakes can cause a trailer skid. The foot brake applies the brakes throughout the combination and should control normal braking.

Source: DC DMV Commercial Driver License Manual — § 6.2.1, “Trailer Hand Valve”

Question 2

When a tractor and semitrailer are correctly coupled, the fifth-wheel jaws close around which part of the kingpin?

  1. A The head
  2. B The polished upper section
  3. C The shank
  4. D The mounting base

Correct answer: C – The shank

During the coupling inspection, look into the back of the fifth wheel and verify that the jaws have closed around the kingpin's shank. Also check that there is no space between the upper and lower fifth-wheel surfaces. If the jaws are improperly positioned, the trailer could separate from the tractor.

Source: DC DMV Commercial Driver License Manual — § 6.4.1, “Coupling Tractor-Semitrailers,” Step 13, “Inspect Coupling”

Question 3

If you discover that the service and emergency air lines were crossed during coupling, what must you do before driving?

  1. A Accelerate until the trailer brakes release
  2. B Continue if the mirrors show no problem
  3. C Turn sharply to check the coupling
  4. D Reconnect the lines correctly and test the trailer brakes

Correct answer: D – Reconnect the lines correctly and test the trailer brakes

Crossed air lines can prevent the trailer tanks from charging and the spring brakes from releasing. On an older trailer without spring brakes, the combination might move even though the trailer brakes do not work. Connect the proper glad hands together and verify trailer-brake operation before driving.

Source: DC DMV Commercial Driver License Manual — § 6.2.5, “Hose Couplers (Glad Hands)”

Question 4

If a trailer begins skidding because its wheels locked during braking, what should you do first?

  1. A Accelerate sharply
  2. B Turn the steering wheel sharply
  3. C Apply the trailer hand valve harder
  4. D Release the brakes to restore traction

Correct answer: D – Release the brakes to restore traction

Locked trailer wheels can cause the trailer to swing outward and begin a jackknife. Release the brakes to let the wheels regain traction. Do not use the trailer hand valve to straighten the rig because the trailer's braking caused the skid; once traction returns, the trailer should begin following the tractor again.

Source: DC DMV Commercial Driver License Manual — § 6.1.5, “Prevent Trailer Skids”

Question 5

A 27-foot, three-axle tractor-semitrailer has less rearward amplification than a 45-foot, five-axle tractor-semitrailer.

  1. A TRUE
  2. B FALSE

Correct answer: B – FALSE

The statement is false. The manual's chart shows the 45-foot, five-axle tractor-semitrailer with lower rearward amplification than the 27-foot, three-axle combination. Greater rearward amplification produces a stronger crack-the-whip effect, increasing the likelihood that the trailer will overturn during a sudden steering maneuver.

Source: DC DMV Commercial Driver License Manual — § 6.1.2, “Steer Gently,” Figure 6.1

Question 6

For the fifth-wheel coupling to be secure, where must the safety latch be positioned?

  1. A Through the locking lever
  2. B Inside the locking lever
  3. C Under the locking lever
  4. D Over the locking lever

Correct answer: D – Over the locking lever

The District of Columbia manual requires the locking lever to be in the lock position and the safety latch to be positioned over it. On some fifth wheels, the catch must be put into place manually. If either part is not correctly positioned, the coupling must be corrected before the vehicle is driven.

Source: DC DMV Commercial Driver License Manual — § 6.4.1, “Coupling Tractor-Semitrailers,” Step 13, “Inspect Coupling”

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