CLP Combination Vehicle Operations 2 — Questions and Answers
Question 1: What is the primary danger of trailer skid (trailer jackknife) in a combination vehicle?
- The trailer swings outward and can hit other vehicles (Correct answer)
- The steering axle loses traction
- The engine overheats from braking
- The fifth wheel disconnects from the kingpin
Correct answer: The trailer swings outward and can hit other vehicles
During a trailer jackknife the trailer swings toward the cab, potentially striking other vehicles or causing a rollover.
Question 2: When should you test the trailer brakes using the hand valve (trolley valve) before a trip?
- At low speed in a safe area before leaving the terminal (Correct answer)
- While driving at highway speed
- Only after a full air pressure build-up on the road
- You should never test trailer brakes separately
Correct answer: At low speed in a safe area before leaving the terminal
Test trailer brakes by applying the hand valve at low speed in a safe area to confirm the trailer brakes are functioning properly.
Question 3: What effect does adding a second trailer (doubles) have on the braking distance compared to a single trailer?
- Braking distance increases significantly due to added weight and rearward amplification (Correct answer)
- Braking distance stays the same as a single trailer
- Braking distance decreases because more brakes are available
- Braking distance is cut in half with a second trailer
Correct answer: Braking distance increases significantly due to added weight and rearward amplification
Doubles have greater overall weight and rearward amplification effects, which substantially increase stopping distance.
Question 4: How do you release the fifth wheel locking jaws to uncouple a trailer?
- Pull the release handle while the trailer landing gear is down and the truck is slightly under the trailer (Correct answer)
- Yank the release handle while driving forward slowly
- Use air pressure to blow the jaws open remotely
- Remove the kingpin with a hammer before pulling the handle
Correct answer: Pull the release handle while the trailer landing gear is down and the truck is slightly under the trailer
The landing gear must support the trailer weight and the truck positioned correctly before pulling the fifth wheel release handle.
Question 5: What is 'rearward amplification' in a triple combination vehicle?
- The tendency of the last trailer to sway more violently than the first trailer during a lane change (Correct answer)
- The increase in engine noise toward the rear of the combination
- Increased braking force applied to rear axles only
- The amplified signal from the rear brake sensors
Correct answer: The tendency of the last trailer to sway more violently than the first trailer during a lane change
Rearward amplification means the last trailer in a triple can sway or tip at a much higher rate than the steering inputs or first trailer movement would suggest.
Question 6: When coupling a tractor to a trailer, at what height should the trailer nose be before backing under it?
- Slightly lower than the fifth wheel height so the fifth wheel rides up onto the trailer plate (Correct answer)
- At the same height as the fifth wheel
- Higher than the fifth wheel so the trailer slides down onto it
- Height does not matter as long as the kingpin is visible
Correct answer: Slightly lower than the fifth wheel height so the fifth wheel rides up onto the trailer plate
The trailer should be slightly lower than the fifth wheel so as the tractor backs under, the fifth wheel raises and engages the kingpin properly.
Question 7: What is the correct procedure if the trailer starts to jackknife during braking?
- Release the brakes immediately to allow the trailer wheels to regain traction (Correct answer)
- Apply more brake pressure to stop the trailer faster
- Accelerate to straighten the trailer
- Steer sharply in the opposite direction of the skid
Correct answer: Release the brakes immediately to allow the trailer wheels to regain traction
Releasing the brakes allows the locked trailer wheels to begin rolling again and regain traction, helping to straighten the combination.
CLP Combination Vehicle Operations 2
What is the primary danger of trailer skid (trailer jackknife) in a combination vehicle?