RoadsideProof
Check your DOT

FMCSA roadside violation code

393.40FBNPB — Brake - Inoperative or missing parking/emergency brake on power unit

Raw code: 39340FBNPB. Description, BASIC, weights, and appearance count below come from the public SMS violations snapshot dated 2026-07-31.

What this code counts in

Raw FMCSA code
39340FBNPB
Description
Brake - Inoperative or missing parking/emergency brake on power unit
Group
Brakes All Others
BASIC
Vehicle Maintenance
Observed severity weight
4. Public FMCSA SMS violations file, snapshot 2026-07-31.
Observed out-of-service addition
0, 2. Public FMCSA SMS violations file, snapshot 2026-07-31.
Appearances in this file
3,028 violation rows. Public FMCSA SMS violations file, snapshot 2026-07-31.

The out-of-service addition varies between records in this file. Use the addition recorded for the violation being calculated.

How time changes the weight

SMS uses a 24-month inspection window. The time weight is ×3 through 6 months back from the snapshot date, ×2 for more than 6 through 12 months back, and ×1 for more than 12 through 24 months back. Older inspections are outside that snapshot's calculation window.

These bands are measured back from the snapshot date in calendar months. At a band boundary, the inspection remains in the more recent band. This describes snapshot calculations, not a promised date for a record to disappear.

Method and band numbers: SMS methodology used for snapshot 2026-07-31; calculation sources and explanation.

The inspection cap

Within each inspection and BASIC, severity weights including any out-of-service additions are summed, capped at 30, and only then multiplied by the time weight. Violations in other BASICs do not enter that cap.

If the sum still reaches the 30-point cap after a violation is removed, the inspection's contribution is unchanged. The effect of removing a violation is the difference between the measure with it and the measure without it, keeping the other snapshot data fixed.

Cap and order of operations: SMS methodology used for snapshot 2026-07-31; how it works.

A worked example for 393.40FBNPB

Illustration using the most frequent observed pair for this code: severity 4 and out-of-service addition 2, recorded together in 3,011 violation rows in snapshot 2026-07-31. Assume no other violations in this BASIC on the inspection. Other records can have different weights.

Inspection severity total: min(30, 4 + 2) = 6. At time weight ×3 it contributes 6 × 3 = 18 to the BASIC numerator; at ×2, 6 × 2 = 12; at ×1, 6 × 1 = 6. These are derived example values using the method for snapshot 2026-07-31.

Pair counts preserve joint observations from the public SMS violations file; they do not identify a carrier or inspection. Formula source: FMCSA SMS methodology v3.21, June 2026, sections 3 and Appendix A.

These example weighted numerator points are not a change in the BASIC measure or estimated position. A reference code does not establish support for a personal report. The measure also depends on its denominator and the other inspections. Read how a violation moves the measure.

Related codes in Brakes All Others

Related codes use the same group and BASIC in snapshot 2026-07-31, ordered by appearances in that file.

Violation codes by BASIC

Look up your carrier’s supported BASIC measures

Live lookup in the app for the USDOT you enter. Illustrative examples are separate from your results.

Unsafe Driving, HM Compliance and Crash Indicator are not included in this lookup.

What this lookup supports

What this lookup supports

Vehicle Maintenance

Reference codes: Available

Listed violations: When data and checks allow

Weighted numerator contribution: When data and checks allow

BASIC measure: When data and checks allow

Estimated position and range: When data and checks allow

Hours-of-Service Compliance

Reference codes: Available

Listed violations: When data and checks allow

Weighted numerator contribution: When data and checks allow

BASIC measure: When data and checks allow

Estimated position and range: When data and checks allow

Controlled Substances/Alcohol

Reference codes: Available

Listed violations: When data and checks allow

Weighted numerator contribution: When data and checks allow

BASIC measure: When data and checks allow

Estimated position and range: When data and checks allow

Driver Fitness

Reference codes: Available

Listed violations: When data and checks allow

Weighted numerator contribution: When data and checks allow

BASIC measure: When data and checks allow

Estimated position and range: When data and checks allow

Unsafe Driving

Reference codes: Available

Listed violations: Not offered

Weighted numerator contribution: Internal calculation only; not in lookup

BASIC measure: Not offered

Estimated position and range: Not offered

HM Compliance

Reference codes: Available

Listed violations: Not offered

Weighted numerator contribution: Not offered

BASIC measure: Not offered

Estimated position and range: Not offered

Crash Indicator

Reference codes: Not offered

Listed violations: Not offered

Weighted numerator contribution: Not offered

BASIC measure: Not offered

Estimated position and range: Not offered

The four supported BASICs require readable snapshot data and a computed measure to list violations or open a report. Estimated positions also require sufficient carrier data and passed publication checks; calibration failure can withhold a position or retain a dated previous estimate. Controlled Substances/Alcohol is subject to these checks too. Missing carrier data, no relevant inspections, no applicable violations and an unavailable calculation are different states. An unavailable result is not a zero or a claim that there are no violations. HM Compliance and Crash Indicator have no report calculation in this product.

Unsafe Driving’s SMS denominator is average power units × utilization factor, which depends on vehicle miles traveled (VMT) and carrier segment (Equation 3–1). Our product lacks the historical power-unit inputs needed to reconstruct and validate that full calculation. It calculates numerator points internally only; Unsafe Driving records, measure and estimated position are not offered in this lookup.

Severity weight is an input. Weighted numerator contribution accounts for time weighting and the inspection cap. The marginal change in a named BASIC measure also depends on its denominator. An estimated percentile compares carriers within a safety event group and must be read with its range. Do not add points across BASICs. SMS calculations are separate from an official safety rating. This is our estimate from public FMCSA data, not an official FMCSA percentile.

FMCSA SMS Methodology v3.21, Chapter 3 Safety rating: 49 CFR 385.3