What 393.52(a) means in plain language
393.52(a) is a vehicle maintenance requirement under Federal Motor Carrier Safety Regulations. The regulation requires that specific components and systems on your commercial vehicle be maintained in safe, functional condition. When an inspector cites you for 393.52(a), they've determined that one or more required parts failed to meet that standard during roadside inspection.
This isn't about a missing inspection sticker or paperwork—it's about the actual physical condition of equipment on your truck. If you've received this citation, an inspector found something during the walk-around that didn't meet maintenance standards.
What our enforcement data actually shows
Our inspection records show that 393.52(a) is relatively uncommon in the enforcement landscape. Across 13 million inspections, we've recorded 68 all-time citations for this code, ranking it #1534 out of 3,036 FMCSR codes by citation volume. In the last 12 months, we've seen zero citations, and zero in the last 90 days.
What stands out sharply is the out-of-service rate. When 393.52(a) is cited, the vehicle is placed out of service 100% of the time—all 68 citations resulted in OOS placement. That's drastically higher than the all-FMCSR average OOS rate of 31.4%. This means inspectors take violations of this code very seriously, and every single citation comes with immediate operational consequences.
Who gets cited most
Our data shows fleets such as J & J Hernandez Inc (USDOT 1929976) and Northwind Transport LLC (USDOT 2090653) with 2 citations each in our all-time database. The remaining citations are distributed among smaller carriers and owner-operators, with most having one citation on record.
When we look at vehicle makes, Freightliners account for 15 of the 68 citations, followed by Ford (10), Peterbilt (7), and Dodge (7). This pattern suggests the violation isn't tied to a specific manufacturer defect but rather to maintenance practices across different truck types and fleet sizes.
How severe is this compared to similar codes
To understand where 393.52(a) sits in the maintenance violation hierarchy, compare it to peer codes in the Vehicle Maintenance category:
393.9(a) (Inoperable required lamps) has been cited 660,737 times with a 15.4% OOS rate. Despite being cited far more frequently, lamps violations result in OOS placement much less often.
396.3(a)(1) (Inspection/repair/maintenance—general) has 236,919 citations with a 45.3% OOS rate. This is a broader maintenance code but still results in OOS placement less than half the time.
393.78 (Windshield condition defective) has 157,894 citations with only a 0.3% OOS rate, showing that some maintenance violations rarely trigger immediate removal from service.
The 100% OOS rate for 393.52(a) places it in the most severe category of maintenance enforcement—every single citation is treated as an immediate safety threat.
How to avoid it
Because of the extreme rarity of citations and the 100% OOS placement rate, prevention starts with a thorough pre-trip inspection routine:
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Perform a complete walk-around before every shift. Check all visible equipment, lights, mirrors, and fasteners. If something looks loose, corroded, damaged, or non-functional, address it before moving.
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Know your truck's maintenance schedule and stay ahead of it. Don't wait for inspector feedback. Your manufacturer and your carrier's maintenance team provide guidance—follow it religiously.
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Document all maintenance performed on your unit. Keep records of repairs, part replacements, and inspections. If questioned at roadside, you can show that work was done properly and recently.
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Address minor issues immediately. A small leak, a worn seal, or a loose component can escalate into a 393.52(a) citation if left unattended. Report problems to your dispatcher or maintenance team without delay.
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Don't assume something "still works." Functional doesn't mean compliant. A light might still illuminate but be dim or misaligned. A brake might still work but have excessive play. An inspection finds the difference.
Given that the top cited vehicle makes include Freightliners, Fords, and Peterbilts, no single truck type is exempt. Maintenance discipline applies equally to all vehicles and all drivers. The 100% OOS placement rate means your next citation for this code will immediately take you out of service—so prevention isn't just about compliance; it's about uptime and your bottom line.