CDL Combination Vehicles TestDriving Combination Vehicles SafelyMedium
A commercial driver is preparing to drive a combination vehicle on a long trip. During the pre-trip inspection, they notice that the fifth wheel locking jaws are not fully closed around the kingpin. What is the correct procedure the driver should follow before starting the trip?
- ADisconnect the trailer, reposition the tractor, and attempt to couple again, ensuring the jaws lock properly.
- BSecure the locking jaws with a chain or strap to prevent accidental uncoupling during transit.
- CProceed with caution, as the weight of the trailer will force the jaws to close during driving.
- DApply grease to the fifth wheel plate and then attempt to pull the trailer forward to force the connection.
Show answer & explanationAnswer & explanation
Correct answer: A. Disconnect the trailer, reposition the tractor, and attempt to couple again, ensuring the jaws lock properly.
Improperly locked fifth wheel jaws mean the trailer is not securely coupled to the tractor, leading to a high risk of uncoupling during transit. The only safe solution is to uncouple and re-couple correctly.
Why the other options are wrong
- B. Chains or straps are not designed to secure the primary coupling mechanism and will not prevent an uncoupling if the jaws are not properly locked.
- C. This is extremely dangerous. The trailer could detach at any time, leading to a catastrophic accident.
- D. Greasing is for friction reduction, not for forcing a connection. Attempting to force it can damage components or still result in an unsafe connection.
Fifth Wheel Coupling Check
Always ensure the fifth wheel locking jaws are fully closed around the kingpin during pre-trip inspection. If not, uncouple and re-couple correctly.
- Jaws must be fully closed.
- Visual inspection is key.
- Re-couple if not secure.
Memory trick: Jaws Not Closed? Re-couple, Don't Lose.