§393.43 requires every towed vehicle (other than a pole trailer or coupled to a converter dolly) to be equipped with brakes acting on all wheels (per §393.42), and requires a means by which the brakes on the towed vehicle will be automatically applied if the towed vehicle breaks away from the towing vehicle. For air-braked combinations, this is the emergency-brake application that occurs on loss of air pressure; for hydraulic-braked trailers, this is the breakaway-cable-actuated emergency brake.
OOS
A non-functional breakaway brake system on a towed vehicle is an OOS condition. The combination cannot continue until the protection is restored — emergency brake application must occur on disconnection of the air or signal line.
Severity weight
Severity weight 6 in the Vehicle Maintenance BASIC. The weight reflects the severity of the failure mode: a runaway trailer in traffic.
How to prevent it
- Include a "yank test" in pre-trip — pull the emergency air line and confirm the trailer brakes apply.
- For hydraulic trailers, the breakaway battery is the failure mode — check it on every pre-trip.
- After any trailer disconnect/reconnect, re-verify breakaway protection before moving.
How Roadworthy HQ helps
A breakaway or emergency-braking citation shows up in Roadworthy HQ as part of the inspection it came from, not as a record of its own: the app does not store individual violation codes. Log the roadside inspection on the vehicle's Inspections tab: date, state, level, driver, the number of violations, and whether it was out-of-service. For an out-of-service inspection the 15-day §396.9(d)(3) repair-certification countdown stays on that tab until you enter the certification date. The rule's 15 days cover every violation on the report, not only out-of-service ones, so for a non-OOS inspection that date is yours to track. The repair itself goes in the vehicle's maintenance log: date, type, what was done, who did it, and cost. DVIRs are logged per vehicle with the defect described in your own words, and a defect marked safety-affecting that is logged without a repair certification sends a critical alert.