Vehicle Inspection and Out-of-Service Criteria Related to Brakes
The inspection and out-of-service domain tests when a brake defect makes a vehicle illegal to drive and how inspectors count defective brakes. The thresholds are both percentage-based and absolute, so one bad steer brake can matter more than several defects elsewhere.
OOS defects
- 20% or more of the service brakes on the power unit or towed unit are defective.
- Any defective service brake on the steering axle is out of service, regardless of percentage.
- Air loss beyond the leakage limit, an inoperative low-pressure warning, or spring brakes that do not apply are out of service.
- A parking brake that will not hold, pushrod travel beyond the adjustment limit, or a cracked drum or rotor is out of service.
Counting examples
- Count service brakes by wheel position on the power unit and towed unit separately.
- A tractor with 6 service brakes and 1 defect has about 17%, below the 20% threshold.
- If that one defect is on the steering axle, the vehicle is out of service anyway.
Worked example
An inspector finds two defective service brakes on a tractor with six service brakes. Two out of six is 33%, which meets the 20% threshold, so the power unit is out of service. If only one brake were defective, it would be about 17% and not out of service by the percentage rule, unless it was a steering-axle brake. The trailer is counted separately, so a trailer with one bad brake out of four is 25% and out of service.
Traps that cost marks
- Applying the 20% rule to the whole combination instead of each unit.
- Passing a vehicle with a defective steering-axle brake because the total is under 20%.
- Ignoring pushrod travel because the brake still stops the vehicle.
- Treating a parking brake that will not hold as a minor defect.
- Out-of-service means do not drive until repaired.