What 178.340-6 means in plain language
FMCSR 178.340-6 covers the structural supports and anchoring systems on MC306, MC307, and MC312 hazardous materials tanker vehicles. These are specialized tank trucks designed to transport liquids and gases under pressure or in bulk. The regulation requires that the tank itself—along with all pipes, valves, and fittings attached to it—be securely mounted to the frame of the truck using supports and anchors that meet specific engineering standards.
If your tank isn't properly supported or the anchoring brackets are loose, corroded, cracked, or missing, you can be cited under this code. Inspectors are looking for visible damage, improper welds, missing bolts, or any sign that the tank could shift or detach during transport. A failure in these supports isn't just a paperwork issue—it directly threatens cargo containment and road safety.
This applies whether you're hauling corrosives, flammables, or other hazmat products. The regulation exists because a tank that shifts or comes loose can create a catastrophic spill, fire, or explosion.
What our enforcement data actually shows
Across our 13 million+ roadside inspection records, 178.340-6 is cited very rarely. We've recorded 7 citations all-time for this code, with 0 citations in the last 12 months and 0 in the last 90 days. This makes 178.340-6 ranked #2312 out of 3,036 FMCSR codes by citation volume—it's one of the least-enforced regulations in the hazmat category.
None of the 7 all-time citations resulted in an out-of-service (OOS) placement. The OOS rate for 178.340-6 is 0.0%, compared to the all-FMCSR average OOS rate of 31.4%. This low OOS rate suggests that when inspectors find support or anchoring issues, they typically treat them as correctable defects rather than immediate safety shutdowns. However, rarity of enforcement does not mean the requirement is lax—it likely reflects that most carriers maintain their tanks properly and that catastrophic failures are caught before they reach the roadside.
Who gets cited most
Our inspection records do not include geographic breakdowns by state for this code. The citation data is distributed across seven different carriers, each with 1 citation all-time. These include SAMUEL CORALUZZO CO INC (USDOT 156123), BASIN WESTERN INC (USDOT 167011), MARKO INVESTMENT CO INC (USDOT 197131), PARKLAND USA CORPORATION (USDOT 227853), JMT CORP (USDOT 961729), DIESEL DOGS FUEL SERVICE INC (USDOT 1060895), and ROTAK LLC (USDOT 3084147). The data shows that this violation is broadly scattered across operators, with no single carrier or region showing a pattern.
On the vehicle side, our data indicates that Heil Co. tanks and Peterbilt tractors together account for 6 of the 7 citations. Kenworth and Freightliner units also appear. This distribution likely reflects the prevalence of these manufacturers in the hazmat tanker fleet rather than a quality or design problem.
How severe is this compared to similar codes
When we look at other hazmat regulations in the same category, 178.340-6 sits at the far mild end of the enforcement spectrum. General loading and unloading violations (codes 177.834A-HMC and 177.834(a)) drive thousands of citations each—3,954 and 3,839 respectively—and carry OOS rates of 99.2% and 97.9%. Placarding violations (177.817(a)) show 2,274 citations with a 75.1% OOS rate. By contrast, 178.340-6's 7 all-time citations and 0.0% OOS rate indicate that this is a low-volume, low-severity violation from an enforcement perspective.
Even within the anchoring and support domain, peer codes like 172.502(a)(1) (general placarding requirements) show 1,820 citations, and 172.516(c)(6) (placarding damaged or obscured) shows 1,796 citations. The rarity of 178.340-6 citations may reflect the fact that modern tanks and carriers have well-established maintenance schedules for these structural elements, or that defects are caught during pre-purchase inspection and repair before the unit reaches a weigh station.
How to avoid it
To stay compliant with 178.340-6, make these checks part of your pre-trip inspection routine:
-
Walk the tank perimeter. Look for cracks, corrosion, loose bolts, or missing hardware on all bracket welds and fasteners that attach the tank to the frame. Pay special attention to corners, lower corners where water collects, and areas near high-stress points.
-
Check for visible damage to supports. Rust, bent metal, or cracked welds are red flags. If a bracket looks compromised, do not move the vehicle—report it to dispatch and your maintenance team.
-
Verify bolts are tight. Vibration during transport can loosen fasteners over time. Use a visual inspection first; if you notice a bolt is missing or hanging loose, it must be replaced or tightened before rolling.
-
Inspect piping and fittings attachment. All hoses, relief valves, and gauges mounted to the tank must be securely anchored. Loose piping can abrade, leak, or detach during rough roads.
-
Report wear early. If you notice corrosion creeping or paint flaking on support welds, tell your fleet safety manager immediately. Early intervention prevents a roadside citation and keeps your tank safe.
-
Maintain pressure test records. Support and anchoring integrity is tied to tank pressure integrity. Keep documentation of hydro tests and repairs in your logbook or fleet system.
Because citations for this code are so rare and none result in OOS placement when they do occur, the risk to your livelihood is low—but the safety risk is real. A tank that separates from its frame or loses cargo is not just a violation; it is a catastrophe. Treat tank support maintenance as a non-negotiable part of fleet operations.