May the information in the stopping distance table be used to determine the stopping distances at speeds greater than 20 mph?

Section § 393.52: Brake performance.

Question 1: May the information in the stopping distance table be used to determine the stopping distances at speeds greater than 20 mph?

Guidance: No, the table is not intended to be used to predict or determine...

Are vacuum gauges required on the vacuum portion of vacuum-assisted hydraulic brakes?

Section § 393.51: Warning signals, air pressure and vacuum gauges.

Question 3: Are vacuum gauges required on the vacuum portion of vacuum-assisted hydraulic brakes?

Guidance: No. Section 393.51(d)(2) requires only that CMVs with vacuum brakes (not...

Is the low pressure warning device required to activate before the tractor protection valve?

Section § 393.51: Warning signals, air pressure and vacuum gauges.

Question 1: Is the low pressure warning device required to activate before the tractor protection valve?

Guidance: No. Section 393.51 does not explicitly require the warning device to...

Are the brakes on a vehicle towed in a driveaway-towaway operation or towed disabled vehicle required to be operable at all times?

Section § 393.48: Brakes to be operative.

Question 3: Are the brakes on a vehicle towed in a driveaway-towaway operation or towed disabled vehicle required to be operable at all times?

Guidance: Section 393.48(c) provides an exception to the requirement...

If a CMV manufactured on or after July 25, 1980 (see § 393.42) has brake components on the front axle, and the brakes are not operable, does the vehicle comply with § 393.48?

Section § 393.48: Brakes to be operative.

Question 1: If a CMV manufactured on or after July 25, 1980 (see § 393.42) has brake components on the front axle, and the brakes are not operable, does the vehicle comply with § 393.48?

Does the term ‘‘rear wheels’’ include the tag axle on a bus/motorcoach?

Section § 393.44: Front brake lines, protection.

Question 1: Does the term ‘‘rear wheels’’ include the tag axle on a bus/motorcoach?

Guidance: Yes. The braking system on a bus/motorcoach must be constructed so that if any brake line to either front wheel...

Are tractor protection valves required by § 393.43(b), or may similar devices be used?

Section § 393.43: Breakaway and emergency braking.

Question 1: Are tractor protection valves required by § 393.43(b), or may similar devices be used?

Guidance: No. Similar devices may be used provided the devices meet the performance requirements of § 393...

§ 393.42(b)(3) of the FMCSRs states that any full trailer, any semitrailer, or any pole trailer having a gross weight of 3,000 pounds or less must be equipped with brakes

Section § 393.42: Brakes required on all wheels.

Question 3: § 393.42(b)(3) of the FMCSRs states that any full trailer, any semitrailer, or any pole trailer having a gross weight of 3,000 pounds or less must be equipped with brakes if the weight of the towed...

Are unladen converter dollies covered by the exemption in § 393.42(b)(2)?

Section § 393.42: Brakes required on all wheels.

Question 2: Are unladen converter dollies covered by the exemption in § 393.42(b)(2)?

Guidance: Yes. However, if the converter dolly is laden, the brakes must be operable.

Do retractable or lift axles have to be equipped with brakes?

Section § 393.42: Brakes required on all wheels.

Question 1: Do retractable or lift axles have to be equipped with brakes?

Guidance: Yes, when the wheels are in contact with the roadway.