What 393.134 means in plain language
FMCSR 393.134 governs how large boulders must be secured when transported on a commercial motor vehicle. The regulation sets out specific requirements for aggregate large boulders — think loose rock loads hauled by dump trucks and similar heavy-haul equipment — and those requirements go well beyond simply piling material into a bed and driving away.
The core concern is mass and unpredictability. Large boulders are irregularly shaped, can shift under braking or cornering, and if one leaves a moving truck it becomes a catastrophic road hazard. The regulation exists because general cargo securement rules were not written with this specific material in mind, so 393.134 fills that gap with its own tailored standards.
For a driver, this means knowing before you roll that each boulder in your load meets the defined criteria for how it must be positioned, contained, or restrained. It is not enough to have the load look stable at the yard. An inspector will evaluate whether the securement method actually meets the rule's specific requirements for boulders of the size you are carrying.
What our enforcement data actually shows
If you just got cited for 393.134, you are almost certainly sitting on the shoulder right now because our inspection records show a 96.8% out-of-service rate for this code — meaning that across all 4,888 all-time citations in our database, 4,734 of those drivers were placed out of service on the spot. That is not a paperwork violation you drive away from.
To put that in perspective, the all-FMCSR average OOS rate across all codes in our database is 31.4%. This code runs more than three times that average. When an inspector flags 393.134, they are almost never issuing a warning and waving you through.
In the last 12 months alone, our records show 813 citations for this code. In just the last 90 days, there were 146 citations — and the monthly trend data tells an important story. Citations peaked at 102 in a single month (July 2025) and have remained consistently elevated, with monthly totals ranging from 59 to 102 across the most recent full months we track. This is an actively enforced code, not a dusty regulation that only surfaces occasionally.
This code ranks #344 out of 3,036 FMCSR codes by citation volume in our database — placing it solidly in the top 12% of all cited regulations.
Who gets cited most
Looking at the last 180 days in our database, Texas leads all states with 286 citations and a 95.1% OOS rate. North Carolina comes in second with 50 citations and a 96.0% OOS rate. Illinois recorded 18 citations with a 100.0% OOS rate — every single inspection in our Illinois data for this period resulted in an OOS order.
The OOS rate variation across these states is relatively tight (less than 5 percentage points between Texas and North Carolina), but Illinois sitting at 100.0% signals that enforcement there treats any 393.134 violation as an automatic OOS event with no discretion.
When it comes to carriers, our data shows fleets such as WASTE MANAGEMENT OF TEXAS INC (USDOT 386083) with 98 all-time citations and BFI WASTE SERVICES LLC (USDOT 962089) with 69 all-time citations appearing most frequently in our records. The concentration of waste-industry carriers in this list reflects the type of material — aggregate and construction debris — that triggers this regulation.
How severe is this compared to similar codes
393.134 is a Vehicle Maintenance category code, so comparing it to peers in that category makes clear just how unusual its OOS rate is. Consider 393.9(a), covering inoperable required lamps, which has 660,737 citations in our database but only a 15.4% OOS rate — a code cited far more often but resulting in far fewer drivers being parked. Or look at 393.78, windshield condition defective, which shows 157,894 citations and only a 0.3% OOS rate. Inspectors routinely write that one up without sidelining the truck.
Even 396.3(a)(1), inspection/repair/maintenance general, which carries 236,919 citations and a 45.3% OOS rate, does not come close to 393.134's 96.8%. Within its peer group, 393.134 is an extreme outlier — a low-volume code that almost always ends in an out-of-service order.
How to avoid it
The co-occurring violation pattern in our 90-day data is a checklist hiding in plain sight. When inspectors cite 393.134, they are also frequently finding other problems on the same truck. Use this pattern to build a tighter pre-trip.
- Verify your boulder securement before you leave the yard. Each boulder must meet the specific positioning and restraint requirements of 393.134. Walk the load, not just the cab. If a boulder can shift, it will shift.
- Check all required lamps front to back. Our data shows 393.9 (inoperable required lamp) appeared in 31 shared inspections in the last 90 days alongside 393.134 citations. A burned-out lamp is what draws an inspector to your truck in the first place.
- Inspect your slack adjusters. 393.47E (slack adjuster defective) appeared in 13 shared inspections. On MACK, Peterbilt, and Kenworth trucks — the three most-cited vehicle makes in our 393.134 data — brake system wear is a known factor. Check pushrod travel at every pre-trip.
- Look at your tires. 393.75A3-TAOL (tires at or below 50% of maximum inflation pressure) showed up in 14 shared inspections. A heavy boulder load accelerates tire stress; check inflation before departure, not at the scale.
- Confirm your periodic inspection paperwork is on the truck. 396.17C (no proof of periodic inspection) appeared in 19 shared inspections. Keep the current inspection certificate in the cab where you can hand it to an inspector immediately.
- Check your steering components. 393.53B (steering system components worn) appeared in 13 shared inspections. Boulder loads create high dynamic stress on front axle components; if steering feels loose, have it checked before the trip.
- Make sure all signals and headlamps work. Both 393.9TS (inoperative turn signal) and 393.9H (inoperable head lamps) each appeared in 13 shared inspections. One non-functioning light gives an inspector a legal reason to pull you over; two puts you at high risk of a full Level 1 inspection that will find your load.
The bottom line from our data: an inspector who stops a boulder-hauling truck for a minor equipment defect will look at the load. If the load doesn't meet 393.134, you are not driving away. A 96.8% OOS rate across 4,888 inspections leaves almost no room for "close enough."