CDL General Knowledge TestCombination Vehicles (if applicable)Easy
A driver is preparing to couple a tractor to a semi-trailer on a slightly sloped surface. What is the most critical initial step to prevent the trailer from moving unexpectedly?
- AInspect the kingpin for any signs of wear or damage.
- BApply the trailer parking brakes and check their hold.
- CEnsure the fifth wheel skid plate is properly lubricated.
- DAdjust the tractor's air suspension to match the trailer height.
Show answer & explanationAnswer & explanation
Correct answer: B. Apply the trailer parking brakes and check their hold.
Before backing under a trailer, it is crucial to ensure the trailer is securely held in place by its parking brakes. This prevents uncontrolled movement during the coupling process, which can lead to serious accidents.
Why the other options are wrong
- A. Kingpin inspection is part of the overall pre-trip but not the primary step to prevent immediate trailer movement.
- C. Lubrication is important for proper coupling but does not prevent trailer movement.
- D. Adjusting suspension is done to align the tractor and trailer, not to prevent trailer roll.
Trailer Securing for Coupling
Before coupling, the trailer must be securely held in place to prevent accidental movement, primarily by its parking brakes.
- Prevents runaways during coupling.
- Ensures driver safety.
- A critical first step in the coupling procedure.
Memory trick: Secure the trailer first, then connect the tractor.