396.3A1BOS

396.3A1BOS Violation: 20 Percent or More Defective Brakes

Twenty percent or more of the service brakes on the vehicle or combination were recorded with out-of-service brake defects.

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Plain-English answer

What does violation code 396.3A1BOS mean?

Twenty percent or more of the service brakes on the vehicle or combination were recorded with out-of-service brake defects.

Why carriers pay attention

How 396.3A1BOS can affect a trucking safety record

This calculation-based code can place the vehicle combination out of service. Every underlying brake defect and the total number of brakes used in the denominator should be checked.

FMCSA inspection data can flow into the Safety Measurement System used to organize carrier performance into Behavior Analysis and Safety Improvement Categories, commonly called FMCSA SMS BASICs. The carrier should verify the inspection, the assigned BASIC, and whether the violation is included in the official calculation.

How it gets cited

Common 396.3A1BOS inspection situations

  • Multiple defective brakes reach or exceed 20 percent of the service brakes on the combination.

  • An underlying defect, axle count, or brake count is recorded incorrectly and changes the calculation.

DataQ review

When a 396.3A1BOS violation may deserve a closer look

A DataQ challenge should identify a specific factual or legal error in the inspection data. These are review questions—not assumptions that the violation should be removed.

Potential review angles

  • One or more underlying brake defects do not meet the applicable out-of-service criterion.
  • The total service-brake count or percentage calculation is wrong.
  • A defect was duplicated or assigned to the wrong vehicle in the combination.

Evidence to collect

  • Inspection worksheet listing every brake and measurement
  • Vehicle configuration and axle/brake count documentation
  • Component-specific technician findings for each cited brake
Compliance expert review

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DataQs changes in 2026

A stronger review process still requires a stronger record.

FMCSA’s 2026 DataQs overhaul adds independent review stages, decision deadlines, and more detailed explanations. Carriers still carry the burden of identifying the error and supporting the requested correction.

See the 2026 DataQs changes
Frequently asked questions

396.3A1BOS violation FAQ

What does a 396.3A1BOS violation mean?

Twenty percent or more of the service brakes on the vehicle or combination were recorded with out-of-service brake defects.

Which FMCSA SMS BASIC is associated with 396.3A1BOS?

Code 396.3A1BOS is commonly associated with the Vehicle Maintenance BASIC in the FMCSA Safety Measurement System. Inclusion and weighting should be confirmed on the carrier’s official record.

Can a trucking company challenge a 396.3A1BOS violation?

A carrier may submit an FMCSA DataQs Request for Data Review when the underlying inspection data is incomplete or incorrect. A repair made after the inspection does not by itself prove the original 396.3A1BOS finding was wrong.

What evidence helps review a 396.3A1BOS violation?

Useful evidence may include inspection worksheet listing every brake and measurement, vehicle configuration and axle/brake count documentation, component-specific technician findings for each cited brake. The best evidence is tied to the cited vehicle, driver, location, and inspection time.

Keep reviewing

Related DOT violation codes

View all violation guides
393.47EBrake Out of AdjustmentBrakes393.48AInoperative or Defective BrakesBrakes393.45B2Brake Hose Chafing or KinkingBrakes393.9Inoperable Required LampLighting

Source references: 49 CFR 396.3 and FMCSA roadside inspection data. This guide is general information and does not guarantee a DataQs outcome or replace legal advice.