Do the FMCSRs specify what type of horn is to be used on a CMV?

Section § 393.81: Horn.

Question 1: Do the FMCSRs specify what type of horn is to be used on a CMV?

Guidance: No.

If a compartment in a CMV is no longer used as a sleeper berth, must it be maintained and equipped as a sleeper berth as required in § 393.76?

Section § 393.76: Sleeper berths.

Question 1: If a compartment in a CMV is no longer used as a sleeper berth, must it be maintained and equipped as a sleeper berth as required in § 393.76?

Guidance: No.

Do tires marked ‘‘NHS’’ (not for highway service) mean that highway use is prohibited by § 393.75?

Section § 393.75: Tires.

Question 4: Do tires marked ‘‘NHS’’ (not for highway service) mean that highway use is prohibited by § 393.75?

Guidance: No, provided the use of such tires does not decrease the safety of operations (see Periodic Inspection...

May tires be filled with materials other than air (e.g., silicone, polyurethane)?

Section § 393.75: Tires.

Question 3: May tires be filled with materials other than air (e.g., silicone, polyurethane)?

Guidance: Section 393.75 does not prohibit the use of tires filled with material other than air. However, § 393.3 may prohibit the use...

May a vehicle transport HM when equipped with retreaded tires?

Section § 393.75: Tires.

Question 2: May a vehicle transport HM when equipped with retreaded tires?

Guidance: Yes. The only CMV that may not utilize retreaded tires is a bus, and then only on its front wheels.

If a CMV has a defective tire, may the driver remove the defective tire from the axle and drive with three tires on an axle instead of four?

Section § 393.75: Tires.

Question 1: If a CMV has a defective tire, may the driver remove the defective tire from the axle and drive with three tires on an axle instead of four?

Guidance: Yes, provided the weight on all of the remaining tires does not...

May a fifth wheel be considered as a coupling device when towing a semi-trailer in a driveaway-towaway operation?

Section § 393.71: Coupling devices and towing methods, driveaway-towaway operations.

Question 1: May a fifth wheel be considered as a coupling device when towing a semi-trailer in a driveaway-towaway operation?

Guidance: Yes. Section 393.71(g) requires...

Section 393.70(d) requires that every full trailer must be coupled to the frame

Section § 393.70: Coupling devices and towing methods, except for driveaway-towaway operations.

Question 3: Section 393.70(d) requires that every full trailer must be coupled to the frame, or an extension of the frame, of the motor vehicle which tows it with one or...

When two safety chains are used, must the ultimate combined breaking strength of each chain be equal to the gross weight of the towed vehicle(s) or would the requirements be met if the combined breaking strength of the two chains is equal to the gross wei

Section § 393.70: Coupling devices and towing methods, except for driveaway-towaway operations.

Question 2: When two safety chains are used, must the ultimate combined breaking strength of each chain be equal to the gross weight of the towed vehicle(s) or would the...

Is there a minimum number of fasteners required to fasten the upper fifth wheel plate to the frame of a trailer?

Section § 393.70: Coupling devices and towing methods, except for driveaway-towaway operations.

Question 1: Is there a minimum number of fasteners required to fasten the upper fifth wheel plate to the frame of a trailer?

Guidance: The FMCSRs do not...