CDL Combination Vehicles Practice Test 2 — Questions and Answers
Question 1: When backing a combination vehicle, why is it always better to back to the driver's side?
- You can watch the rear of your trailer through the side window (Correct answer)
- It is required by federal law
- It keeps the trailer wheels off the shoulder
- It reduces fuel consumption while reversing
Correct answer: You can watch the rear of your trailer through the side window
Backing to the driver's side lets you see the trailer's position by looking out the side window, while sight-side backing avoids blind-side guesswork.
Question 2: What is offtracking in a combination vehicle?
- When the trailer brakes lock before the tractor brakes
- When the rear wheels follow a tighter path than the front wheels in a turn (Correct answer)
- When the trailer drifts sideways on ice
- When the fifth wheel slides out of position
Correct answer: When the rear wheels follow a tighter path than the front wheels in a turn
Offtracking (cheating) occurs because the rear wheels follow a different, tighter path than the front wheels during a turn, so you must swing wide as needed.
Question 3: To avoid hitting an object on the right when turning a corner with a long combination vehicle, you should:
- Turn wide as you complete the turn
- Turn wide as you start the turn (Correct answer)
- Back up before turning
- Keep the trailer wheels on the curb
Correct answer: Turn wide as you start the turn
Keep the rear of the vehicle close to the curb and turn wide only as you complete the turn, so you do not swing into traffic or lose sight of the rear.
Question 4: What does a converter dolly with a single axle and no brakes of its own rely on for stopping?
- Its own spring brakes
- The brakes of the trailers it connects (Correct answer)
- Engine compression only
- A separate air tank
Correct answer: The brakes of the trailers it connects
A converter dolly is used to connect trailers and its braking is integrated through the air lines of the trailers it couples.
Question 5: Which trailer should be loaded first and placed closest to the tractor in a doubles combination?
- The lightest trailer
- The heaviest trailer (Correct answer)
- The trailer with the converter dolly
- Either, weight does not matter
Correct answer: The heaviest trailer
The heavier trailer should be in front (closest to the tractor) to improve handling and reduce trailer sway.
Question 6: When uncoupling, before you disconnect the fifth wheel you should:
- Release the trailer air supply and lower the landing gear (Correct answer)
- Drive forward sharply
- Disconnect the air lines first only
- Raise the landing gear fully
Correct answer: Release the trailer air supply and lower the landing gear
Lower the landing gear until it supports the trailer and set the trailer brakes before pulling the fifth-wheel release handle.
Question 7: A 'kingpin' is the part of a combination vehicle that:
- Locks into the fifth wheel of the tractor (Correct answer)
- Connects the brake chambers
- Holds the landing gear in place
- Secures the mud flaps
Correct answer: Locks into the fifth wheel of the tractor
The kingpin is the steel pin on the trailer that locks into the fifth-wheel jaws of the tractor.
CDL Combination Vehicles Practice Test 2
When backing a combination vehicle, why is it always better to back to the driver's side?