CDL Combination Vehicles TestDriving Combination Vehicles SafelyMedium
During a pre-trip inspection of a combination vehicle, a driver finds that the fifth wheel locking jaws are not fully closed around the kingpin. What is the immediate and most critical action the driver should take?
- AProceed with caution, as long as the trailer air lines are connected.
- BDo not move the vehicle; re-couple the trailer immediately.
- CAttempt to manually force the locking jaws closed with a tool.
- DDrive slowly to a maintenance shop for repair.
Show answer & explanationAnswer & explanation
Correct answer: B. Do not move the vehicle; re-couple the trailer immediately.
An improperly coupled fifth wheel is extremely dangerous and can lead to the trailer separating from the tractor. The vehicle must not be moved until the coupling is secure.
Why the other options are wrong
- A. Proceeding with an unsecured fifth wheel is a major safety violation and extremely dangerous, risking trailer separation.
- C. Attempting to force locking jaws closed with a tool is likely ineffective, could damage components, and doesn't address the underlying coupling issue.
- D. Driving to a shop with an unsecured trailer is highly dangerous and could cause an accident before reaching the destination.
Fifth Wheel Coupling Check
Before moving a combination vehicle, ensure the fifth wheel locking jaws are fully closed around the kingpin, confirming a secure connection.
- Visual inspection is key.
- Locking jaws must be fully engaged.
- An unsecured coupling is highly dangerous.
Memory trick: Locking jaws tight, or no drive tonight.