What 393.134B3 means in plain language
FMCSR 393.134B3 requires that aggregate large boulders be secured according to specific cargo securement rules. If you're hauling rock, aggregates, or similar materials in boulder form, the federal regulation mandates that these items be properly tied down, blocked, or otherwise prevented from shifting, falling, or coming loose during transport.
This isn't about loose gravel or standard aggregate—it's about large boulder-sized material that poses a heightened risk if it breaks free. The regulation exists because an unsecured boulder can shift during braking, cornering, or acceleration, potentially damaging your vehicle, cargo, or other property on the road.
What our enforcement data actually shows
Across our 13 million+ inspection records, 393.134B3 is a relatively rare citation—192 all-time and 79 in the last 12 months—ranking it #1227 out of 3,036 FMCSR codes by citation volume. But here's what makes this violation serious: our data shows a 97.9% out-of-service rate, meaning if you get cited for this, you have an extremely high likelihood of being placed out of service on the spot. That's dramatically higher than the all-FMCSR average OOS rate of 31.4%.
In the last 90 days, we recorded 14 citations for this code. Over the past 12 months, the monthly trend shows activity ranging from 1 to 11 citations per month, with a notable spike in January 2026 (10 citations, all resulting in out-of-service status).
Who gets cited most
Our inspection records show three states account for the majority of recent citations:
- Iowa: 14 citations in the last 180 days with a 100.0% out-of-service rate
- North Carolina: 9 citations with an 88.9% out-of-service rate
- Kentucky: 8 citations with an 87.5% out-of-service rate
All three states show near-universal out-of-service placement, indicating inspectors treat this violation as a critical safety issue across different jurisdictions.
Data shows fleets such as BFI Waste Services LLC account for 8 citations (USDOT 962089) and Waste Industries USA with 4 citations (USDOT 198696). This pattern reflects that aggregate and waste haulers represent a significant portion of 393.134B3 enforcement, though the absolute citation count remains low.
How severe is this compared to similar codes
393.134B3 sits in the Vehicle Maintenance category but operates in a very different enforcement context than peer codes. For comparison:
- 393.9 (Inoperable Required Lamp) has 180,097 all-time citations with only a 6.9% OOS rate—roughly 25 times more common but far less likely to result in roadside removal.
- 396.3(a)(1) (Inspection/Repair/Maintenance - General) has 236,919 citations with a 45.3% OOS rate—more common and more likely to trigger out-of-service than typical maintenance violations, but still less severe than 393.134B3.
- 393.78 (Windshield Condition Defective) has 157,894 citations with a 0.3% OOS rate—nearly universal non-removal despite high enforcement.
The 97.9% OOS rate for 393.134B3 places it at the extreme end of cargo and safety enforcement. Inspectors treat unsecured large boulders as a vehicle control and road safety hazard that cannot be ignored.
How to avoid it
If you haul aggregate, rock, or similar bulk materials, prevention starts with a rigorous pre-trip and loading routine:
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Inspect tiedowns, straps, and chains before every load. Our data shows that 393.104F3 (damaged tiedowns) co-occurs in recent inspections. Check for fraying, rust, bent D-rings, and wear. Replace any strap or chain showing age before you load.
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Use appropriate restraint for boulder-sized material. Don't rely on gravity or box sides alone. Use cross-chains, binder straps, or engineered blocking to prevent any piece from shifting or rolling. Verify the load is stable by hand-testing (carefully) before departing.
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Maintain your vehicle's structural integrity. Our top-cited vehicle makes for this code include Mack (78 citations), Kenworth (23), Peterbilt (21), and International (17). Ensure your stake pockets, D-rings, and frame are not cracked, bent, or corroded. A weak attachment point will cause a tiedown to fail under load.
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Plan your route for smooth driving. Harsh braking, hard cornering, and fast acceleration shift loads. Know where you're going, avoid construction zones and heavy traffic when possible, and drive predictably. Look for no-stop opportunities on highways.
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Double-check after loading and mid-trip. A load can shift during the first few miles. Pull over after 5–10 miles and visually confirm your tiedowns are still tight and your load hasn't moved. If you're on a long haul, inspect again at fuel stops.
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Verify your inspection paperwork is current. Our data shows that 396.17C (No proof of periodic inspection) co-occurs in recent inspections. An out-of-date vehicle inspection won't prevent a cargo securement violation, but an in-service vehicle with current certifications signals to inspectors that you're maintaining standards across the board.
The 97.9% out-of-service rate leaves no room for borderline securement practices. Treat every boulder like it could roll into traffic if not restrained.