What 397.15B-HMDP means in plain language
FMCSR 397.15B-HMDP prohibits fueling a commercial motor vehicle while the engine is running and the vehicle is transporting hazardous materials. The regulation exists because fueling an idling hazmat vehicle creates unnecessary ignition risk—static electricity, sparks, or engine heat can ignite fuel vapors or the hazmat cargo itself.
This is a bright-line rule: if your engine is on and you're carrying hazmat, you must not fuel the vehicle. It doesn't matter if you're "only topping off" or if you believe the specific hazmat load is fire-resistant. The regulation is absolute.
When an inspector observes or has evidence that you fueled while the engine ran during a hazmat transport, they will cite you. The violation is straightforward: engine running + fueling + hazmat load = citation.
What our enforcement data actually shows
Across 13 million inspections in our database, 397.15B-HMDP appears as one of the rarest citations on record. We have logged all-time 1 citation for this code, with 1 citation in the last 12 months and 0 citations in the last 90 days. That places 397.15B-HMDP at #2796 of 3,036 FMCSR codes by citation volume.
The out-of-service (OOS) rate for this code is 0.0%—meaning the single citation in our database did not result in an out-of-service order. For context, the all-FMCSR average OOS rate is 31.4%, so this code's OOS rate is significantly below that baseline. This suggests that when inspectors cite 397.15B-HMDP, they typically treat it as a warning-level infraction rather than a vehicle safety disqualifier.
However, rarity does not mean lenience. The code carries a CSA Severity Weight of 7, indicating moderate regulatory seriousness. The low citation count reflects either strict driver compliance or inconsistent roadside detection rather than regulatory permissiveness.
Who gets cited most
Our inspection records show that in the last 180 days, Florida accounts for 1 citation of 397.15B-HMDP with an OOS rate of 0.0%. With such limited enforcement volume nationwide, geographic variation is not material.
Among carriers, our data shows fleets such as Tampa Bay Mobile Fueling Inc (USDOT 4159770) with 1 all-time citation. This single data point should not be construed as a pattern; it reflects the rarity of this violation across the commercial trucking industry.
How severe is this compared to similar codes
Within the Hazardous Materials category, 397.15B-HMDP sits at the low end of enforcement frequency and OOS severity. For comparison:
- 177.834A-HMC (General loading/unloading hazmat) has 3,954 citations with a 99.2% OOS rate—nearly 4,000 times more enforcement volume and almost guaranteed out-of-service consequences.
- 177.817(a) (Placarding violation) has 2,274 citations with a 75.1% OOS rate—also far more prevalent and much more likely to pull a vehicle off the road.
- 172.602(c)(1) (Maintenance/accessibility of Emergency Response information) has 1,464 citations but a 0.0% OOS rate, matching 397.15B-HMDP's OOS outcome, though it is cited roughly 1,400 times more frequently.
The stark difference in citation volume suggests that improper fueling procedure—while a genuine safety concern—is either actively prevented by most drivers and carriers or simply less visible to inspectors than placarding or packaging violations.
How to avoid it
The rule is simple to follow if you make it a habit:
- Turn off the engine before fueling, regardless of the fueling station's procedures or your schedule pressure. Make this your non-negotiable pre-fueling step every time.
- Use a checklist: before pulling up to any pump while carrying hazmat, confirm your engine is off, parking brake is set, and hazard lights are on (if the station requires them). Treat this as a pre-trip inspection item.
- Communicate with fueling attendants: let them know you're carrying hazmat and your engine is off. This prevents them from starting your engine or hand-signaling you to do so.
- Know your vehicle's fuel system: some older vehicles or those with auxiliary power units (APUs) may have secondary engine systems that idle automatically. Familiarize yourself with your truck's design and disable any automatic idle features before arriving at the pump while loaded with hazmat.
- Train on hazmat transport rules: if you're new to hazmat driving, take a refresher on FMCSR Part 397 before your next load. The rules are not always intuitive, and a brief review prevents costly citations.
The single citation in our 13 million inspection records demonstrates that this violation is rare—but that also means you can make it rarer by treating engine-off fueling as automatic behavior, not a negotiable convenience.