What 393.136F-CLB means in plain language
FMCSR 393.136F-CLB addresses the proper securement of large boulders that don't have a cubic shape and have an unstable base. When you're hauling this type of cargo, the regulation requires that your load be secured in a way that prevents it from shifting, rolling, or falling during transport.
Non-cubic shaped boulders present a specific challenge: their uneven surfaces and unstable bases make them prone to movement. The securement method you use must account for the boulder's irregular geometry and ensure it remains stable throughout your journey, regardless of road conditions, braking, or turning forces.
This is distinct from securing standard cubic or regularly shaped loads. The inspector looking at your vehicle is evaluating whether your chains, straps, blocking, or other securement devices are positioned and tensioned in a way that actually prevents movement of that particular boulder's shape and weight distribution.
What our enforcement data actually shows
Across our 13 million+ inspection records, 393.136F-CLB is exceptionally rare. We have recorded only 5 all-time citations for this violation. In the last 12 months, our database shows 1 citation. In the last 90 days, there were 0 citations.
What stands out is the out-of-service rate: every single citation on record—5 out of 5—resulted in the vehicle being placed out of service. That's a 100.0% OOS rate. For context, the all-FMCSR average out-of-service rate is 31.4%, so this code's enforcement is far more severe on average. This indicates that when inspectors cite this violation, they are finding securement failures serious enough to remove the vehicle from service immediately.
393.136F-CLB ranks #2406 of 3,036 FMCSR codes by citation volume, reflecting how specialized and uncommon this cargo type and violation are.
Who gets cited most
Our inspection records do not include state-level breakdowns for this code. However, our data shows fleets such as Bumpers Construction & Trucking Co Inc (USDOT 537978) with 2 citations and UMS Heavy Equipment Rental Inc (USDOT 2349306) with 1 citation. These carriers operate in the heavy equipment and quarry transport sector, where boulder loads are routine.
The vehicle makes cited most frequently are NUTT and WSTR, each appearing twice in our enforcement history. This small sample reflects the extreme rarity of the violation, but suggests that specialized heavy-haul and equipment trailers have been the focus of enforcement.
How severe is this compared to similar codes
Within the Vehicle Maintenance category, boulder securement violations stand out as dramatically more enforced with out-of-service outcomes compared to many peer codes.
393.9(a) — Inoperable required lamps — has 660,737 citations but only a 15.4% OOS rate. 396.3(a)(1) — Inspection/repair/maintenance general — has 236,919 citations with a 45.3% OOS rate. 393.78 — Windshield condition defective — has 157,894 citations with just a 0.3% OOS rate.
The 100.0% OOS rate for 393.136F-CLB, despite its low absolute volume, underscores that securement failures for unstable, non-cubic loads are treated as critical safety issues. When they do occur, enforcement is absolute and immediate.
How to avoid it
Before you load the boulder:
- Inspect the boulder's shape and base for stability. Mark any flat surfaces, contact points, or areas where it will rest on the trailer deck or blocking.
- Verify that your trailer has adequate blocking, cradles, or custom supports designed for non-cubic loads. Do not assume standard rectangular blocking will work.
- Measure and document the boulder's dimensions and weight distribution if possible, so you understand its center of gravity.
During loading:
- Position the boulder so its most stable face or side is down. Avoid placing it on a rounded or irregular surface that will roll or shift.
- Use chains or straps rated for the full weight and positioned to account for the boulder's actual shape, not its theoretical cubic envelope.
- Add blocking, wedges, or adjustable supports on all sides where movement is possible. Fill gaps between the boulder and trailer.
Before departure:
- Pull and tug on the load from multiple angles. A non-cubic boulder should not move at all, even under significant hand force.
- Walk around and visually confirm that blocking is snug and that chains or straps are tight and positioned to prevent rolling or lateral shift.
- If the boulder is resting on only two or three contact points due to its shape, reinforce those points with additional blocking to prevent rocking.
On the road:
- Drive smoothly. Avoid sudden acceleration, hard braking, or aggressive turns that could destabilize an improperly secured load.
- After the first 50 miles, pull over and re-inspect the load and securement. Vibration and settling can loosen chains or allow blocking to shift.
This violation is rare precisely because most boulder haulers use proper securement. Treat every non-cubic, unstable-base load as a special case requiring custom securement planning, not a standard routine.