Combination Vehicles · Coupling and Uncoupling
Under 49 CFR 393.70(b)(2), what must every fifth wheel assembly have to prevent the tractor and trailer from separating during normal operation?
1.A locking mechanism that prevents separation unless a positive manual release is activatedCorrect answer
2.A backup hydraulic cylinder that reinforces the primary locking jaws underneath the assembly
3.A federally mandated inspection sticker that must be renewed every single 90 days
4.A secondary fifth wheel mounted directly beneath the primary fifth wheel assembly itself
Explanation
49 CFR 393.70(b)(2) requires every fifth wheel assembly to have a locking mechanism that prevents the tractor and trailer from separating unless a positive manual release is activated. This is exactly what the coupling procedure checks for when it has the driver confirm the release arm is properly seated and the safety latch or lock is engaged before backing under a trailer, and then, after coupling, that the jaws have closed on the kingpin. A backup hydraulic cylinder and a second fifth wheel are hardware this regulation does not require. An inspection-sticker requirement does not exist in this equipment regulation.
Source: 49 CFR 393.70(b)(2)
Related Coupling and Uncoupling questions
- After backing the tractor under a trailer and confirming the fifth wheel has locked onto the kingpin, what should the driver do next to check that the coupling is secure?
- After supplying air to a newly coupled trailer and confirming normal air pressure, how does the manual say a driver should confirm the trailer's brakes are working before driving away?
- Under 49 CFR 393.70(d), what is required, in addition to the tow-bar itself, when towing a full trailer or converter dolly?