Violation code

393.91-FS

Motor Coach or other Passenger carrying vehicle equipped with prohibited non-automatically folding seats in the aisle

Vehicle Maintenance2Non-OOS· SMS Appendix A v3.20

393.91-FS is a Cab, Body, Frame violation under 49 CFR §393.91-FS. It falls in the Vehicle Maintenance BASIC with a severity weight of 2/10. Nationally it was cited 75 times in the last five years, with an OOS rate of 58.7%.

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National roadside inspection stats

as of 7/20/2026

Inspections

that found this code

Violations

total written

OOS rate

58.7%

44 OOS

Source: FMCSA roadside inspection data (last 5 years). The OOS rate is the share of these violations that led the officer to mark the driver or vehicle out of service.

Violation group: Cab, Body, Frame
Regulation §: 393.91-FS
Severity weight: 2
Used in SMS: Yes
Status: Active
Updated: 7/20/2026

Last updated July 2026

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Notes

DSMS: Y | Comment: Added in 3.0.4 | Footnote: This violation took effect in SMS as of August 28, 2015.

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Challenging 393.91-FS through FMCSA DataQs

If this violation was written incorrectly, here are the angles trucking-safety managers use to contest it. Playbook: Vehicle Maintenance (general).

Common ways to challenge this code

Pre-trip inspection showed compliant brakes
The driver's pre-trip DVIR documented compliant brake adjustment and operation. The cited defect arose en route or was misclassified at roadside.
Evidence that wins
- ✓Driver Vehicle Inspection Report (DVIR) from that date
- ✓Repair invoice or shop record
- ✓Post-citation re-inspection certificate (clean)
Momentary failure exception (§393.9)
The required lamp was inoperative only momentarily due to vibration, temperature, or similar transient cause — explicitly exempted under §393.9.
Evidence that wins
- ✓Photograph showing the lamp operable before / after the stop
- ✓Repair invoice if a fuse or bulb was replaced
Tread measurement disputed
The tread depth measurement was taken at a worn point that is not representative, contrary to NHTSA/FMCSA measurement standards.
Evidence that wins
- ✓Independent tread gauge reading from same tire (multiple positions)
- ✓Photograph of the tire with a reference scale
Documented maintenance schedule disproves the defect
Carrier's periodic-inspection records show the cited defect could not reasonably have existed at the time of inspection.
Evidence that wins
- ✓Periodic inspection certificate (§396.17)
- ✓Maintenance work order proximate to inspection date

Common pitfalls — avoid these

⚠DataQs cannot remove a violation simply because the defect was repaired after the stop

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More codes in Vehicle Maintenance

Same BASIC category — ranked by national citation volume

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Other Cab, Body, Frame codes

Codes under the same FMCSA violation group

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Frequently asked questions about 393.91-FS

What does violation 393.91-FS mean?

393.91-FS is the FMCSA roadside-inspection violation code for "Motor Coach or other Passenger carrying vehicle equipped with prohibited non-automatically folding seats in the aisle", part of the Cab, Body, Frame group, cited under 49 CFR §393.91-FS.

What BASIC does 393.91-FS affect?

393.91-FS falls under the Vehicle Maintenance BASIC in the FMCSA Safety Measurement System (SMS).

What is the CSA severity weight of 393.91-FS?

393.91-FS carries a severity weight of 2 out of 10. Higher weights indicate violations more closely tied to crash risk, and they count more toward a carrier's Vehicle Maintenance score.

Is 393.91-FS an out-of-service (OOS) violation?

No. 393.91-FS is not an out-of-service violation, so on its own it does not trigger an out-of-service order at the roadside.

How many CSA points does 393.91-FS add to a carrier's score?

The point contribution of 393.91-FS depends on its severity weight (2/10) multiplied by a time weight of 3, 2, or 1 based on how recent the inspection is. You can calculate the exact contribution with the CSA points calculator.

Can 393.91-FS be challenged through DataQs?

Yes. If you believe 393.91-FS was recorded in error, you can file a Request for Data Review (RDR) through the FMCSA DataQs system with supporting evidence. A successful challenge can remove or correct the violation on your record.

Keep going

CSA points calculator How to challenge a violation Draft a DataQs letter for 393.91-FS Vehicle Maintenance BASIC Carrier CSA lookup CSA glossary

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