What 392.4A-POS means in plain language
FMCSR 392.4A-POS is a citation for operating or attempting to operate a commercial motor vehicle while under the influence of, or actively using, a controlled substance or any substance that impairs your ability to safely operate the vehicle. This covers illegal drugs, misused prescription medications, and any other substance that renders you incapable of safe operation.
The regulation doesn't require proof of impairment from a specific test—it can be based on an officer's direct observation of behavior, statements, physical signs, or the discovery of drug paraphernalia or substances in your possession during the inspection. The citation reflects a judgment that your condition at the time of inspection made safe operation impossible.
What our enforcement data actually shows
Across our 13 million+ inspection records, 392.4A-POS is not among the most-cited codes—it ranks #835 of 3,036 FMCSR codes by citation volume. However, its enforcement is extraordinarily harsh. Our data shows an out-of-service rate of 97.6%: of 655 all-time citations, 639 drivers were placed immediately out of service and 16 were not.
For context, the all-FMCSR average out-of-service rate is 31.4%. This code's 97.6% OOS rate is 3.1 times higher, reflecting the zero-tolerance posture inspectors take toward drug use.
In the last 12 months, we recorded 353 citations for 392.4A-POS. Over the past 90 days, that number was 67. The monthly trend shows peaks in May 2025 (52 citations) and June 2025 (41 citations), with a general decline through early 2026.
Who gets cited most
Our data shows enforcement is concentrated in a small number of states. Iowa leads by citation count with 61 citations in the last 180 days—all 61 resulted in out-of-service placement (100% OOS rate). Texas follows with 41 citations, also at a 100% OOS rate. New Mexico had 18 citations with a 94.4% OOS rate, and North Carolina and Illinois round out the top five with 8 and 3 citations respectively, both at 100% OOS rates.
The consistency of the 100% OOS rate across these top states underscores that inspectors and enforcement agencies treat this violation as categorically disqualifying—there is virtually no discretion in the field.
Regarding carriers, our data shows fleets such as NEW PRIME INC (USDOT 3706) with 4 citations and BIG LEAGUE MOVERS INC (USDOT 1999318) with 3 citations across our all-time database. These numbers reflect the incidents recorded in our system and do not imply systemic negligence; they document where enforcement has occurred.
How severe is this compared to similar codes
392.4A-POS sits within a family of controlled-substance and alcohol-related violations. Comparing it to related codes shows the severity spectrum:
- 392.4A-DOSP (Use of drugs) has 3,947 citations with a 95.9% OOS rate—higher volume, similar severity.
- 392.4(a) (Use of drugs) has 3,919 citations and a 96.9% OOS rate—also a high-enforcement variant.
- 392.5(a)(2) (BAC 0.04+) has 778 citations but a 99.2% OOS rate—lower volume but even more consistent out-of-service placement.
All of these codes are enforced with near-universal out-of-service placement, confirming that any substance-related violation triggers immediate removal from the road.
How to avoid it
The most direct way to avoid a 392.4A-POS citation is straightforward: do not operate a commercial vehicle while using, or under the influence of, any controlled substance or impairing substance.
Beyond that, our data reveals patterns worth understanding:
Prescription and over-the-counter medication: Our inspection records show that 392.4A-POS frequently co-occurs with 392.2RG (Operating a CMV while ill or fatigued)—12 shared inspections in the last 90 days. If you take prescription medications that cause drowsiness, dizziness, or impaired concentration, you are not fit to operate. Before starting your shift, review all medication labels. If there is any warning about operating machinery or driving, do not drive that day. Notify your dispatcher and seek an alternative assignment.
Pre-trip inspection vigilance: Co-occurring citations include 393.9 (Inoperable Required Lamp) and 393.78 (Windshield condition defective). Inspectors who stop you are looking closely at your vehicle and your behavior. Ensure your truck passes a thorough pre-trip so you are not stopped in the first place. A clean vehicle reduces the likelihood of a roadside inspection that might escalate to observation of your impairment.
Vehicle make reality check: Our data shows citations across all major truck makes—Freightliner (165), International (113), Utility (49), Kenworth (45), and Volvo (39) are the most cited. No vehicle type exempts you. Regardless of truck brand, the same standard applies.
Fatigue management: Because 392.4A-POS co-occurs with fatigue violations (12 inspections with 392.2RG in the last 90 days), do not operate when drowsy or exhausted. Fatigue impairs judgment and reaction time similarly to drugs. Plan your route to include mandatory rest. If you feel impaired by fatigue, illness, or any substance, find a safe place to stop and rest. Your life and others' lives depend on it.
Zero tolerance mindset: With a 97.6% out-of-service rate, this citation is not something you recover from on the roadside. It is a terminal event for that run and potentially for your career. The cost—immediate removal, likely medical evaluation, potential license suspension, and employment consequences—makes avoidance the only rational strategy.