What 392.4A-DOSU means in plain language
A 392.4A-DOSU citation indicates that a law enforcement officer or roadside inspector found evidence that you were using a controlled substance or were under the influence of any substance that impaired your ability to safely operate a commercial motor vehicle. This is not about prescription medications taken as directed—it targets actual use or impairment that creates a safety risk on the road.
The violation applies whether the substance is illegal, prescription, or over-the-counter. What matters to inspectors is whether the substance rendered you incapable of driving safely. This can include stimulants, depressants, hallucinogens, or any compound that affects your judgment, reaction time, coordination, or alertness behind the wheel.
This is a federal safety violation, not just a state traffic law issue. It appears in your CSA (Compliance, Safety, and Accountability) record and affects your carrier's Safety Measurement System scores, which insurers and freight brokers review when deciding whether to work with your fleet.
What our enforcement data actually shows
Across our 13 million roadside inspection records, we have logged 1,648 all-time citations for 392.4A-DOSU. In the last 12 months, that number reached 1,119 citations. Over the last 90 days alone, inspectors documented 198 citations for this violation.
This code ranks #582 out of 3,036 FMCSR codes by citation volume—not the most common, but far from rare. What makes it urgent is the out-of-service rate: our data shows that 98.5% of all 392.4A-DOSU citations result in immediate out-of-service placement. That means 1,623 drivers were removed from service out of 1,648 total citations. By comparison, the all-FMCSR average out-of-service rate is 31.4%, making 392.4A-DOSU more than three times more likely to trigger an immediate removal.
The 90-day trend shows 198 citations, while the 12-month total of 1,119 suggests enforcement activity has remained steady or elevated throughout the past year.
Who gets cited most
Our inspection records show the highest citation concentrations in three states over the last 180 days: Georgia with 109 citations, Maryland with 31 citations, and South Carolina with 27 citations. All three states show out-of-service rates at or near 100%, indicating zero tolerance in enforcement.
Among fleets in our database, our data shows carriers such as Penske Truck Leasing Co LP and Federal Express Corporation with 4 citations each across their operations, and Cobra Inc, Forever Young Rental Enterprises Incorporated, Western Express Inc, Delgado Logistics LLC, Nova Freight LLC, Stevens Transport Inc, Meyer Logistics Inc, and Pres Ent LLC each with 3 citations. These numbers span years of records and represent a small fraction of their total fleet miles, but the severity of each citation—nearly automatic out-of-service placement—means even one citation creates significant operational disruption.
How severe is this compared to similar codes
In the Controlled Substances/Alcohol category, 392.4A-DOSU sits among the most serious violations. The peer code 392.4A-DOSP (Use of drugs) has 3,947 citations with a 95.9% out-of-service rate—higher volume but similar enforcement intensity. The code 392.5A2-IP (possession or use of alcohol while on duty) shows 691 citations with a 99.0% out-of-service rate, and 392.5(a)(2) (BAC 0.04+) has 778 citations with a 99.2% out-of-service rate.
All of these codes cluster above 95% out-of-service placement, reflecting federal policy that impairment behind the wheel is non-negotiable. 392.4A-DOSU's 98.5% rate places it among the harshest-enforced safety violations in the system.
How to avoid it
Prevention starts before you leave the lot and continues through your entire trip:
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Declare all medications and substances to your employer and medical examiner during your annual DOT physical. Our co-occurring violation data shows that 21 citations in the last 90 days paired this code with invalid or missing medical certificates, suggesting incomplete disclosure of medications. If you take prescription opioids, sedating antihistamines, or other CNS-active drugs, document them and work with your carrier's safety team to manage your schedule around side effects.
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Never operate a vehicle while fatigued or ill. Our data shows 392.2-SLLSR (failure to maintain proper records of duty status) and 392.2-SLL (operating while fatigued) co-occur with 392.4A-DOSU citations in 21, 14, and other multiple instances over the last 90 days. Fatigue and illness impair you similarly to drugs. If you are tired, stop. If you are sick, report off duty.
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Maintain your pre-trip inspection routine. Nineteen citations co-occurred with 396.17C-PI (no proof of periodic inspection) in the last 90 days. While vehicle condition does not prevent drug use, a thorough daily walkthrough keeps your mind engaged and alert, and establishes a habit of noticing your own condition—including signs of impairment.
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Be especially vigilant if you operate a Freightliner, International, or Ford unit. Our vehicle data shows Freightliners account for 360 of the 1,648 all-time citations, International for 206, and Ford for 140. This likely reflects market share, but it means if you drive one of these makes, you are statistically more likely to be inspected. Assume heightened scrutiny and maintain zero tolerance for any substance use.