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How Much Alcohol Can a Truck Driver Legally Have in Their System?

There are few people capable of causing more carnage than an intoxicated truck driver. In an effort to prevent that from happening, the federal government imposes heavy restrictions on alcohol consumption by commercial drivers, including lowering the legal intoxication limit for truck drivers with respect to alcohol. So what is a truck driver's maximum legal BAC?

Answer: A truck driver's maximum legal blood-alcohol concentration (BAC) is 0.00.

Now, this topic is complicated by a belief that the legal limit for a trucker is 0.04. As we'll demonstrate below, that belief is incorrect. We will show what the regulations say, how people have misinterpreted them, and why our interpretation is the better one.

Let's start by examining the relevant regulations.

The Rule

No driver shall report for duty or remain on duty requiring the performance of safety-sensitive functions while having an alcohol concentration of 0.04 or greater. No employer having knowledge that a driver has an alcohol concentration of 0.04 or greater shall permit the driver to perform or continue to perform safety-sensitive functions.

49 CFR § 382.201

Most people will look at the above regulation and will erroneously take it to mean that a truck driver can legally operate a Commercial Motor Vehicle (CMV) if they have, say, a 0.03 BAC. Indeed, many practice guides and "how to litigate a truck accident case" programs will tell you that a trucker with a 0.03 BAC is within the rules. The fact that the regulation specifically states "0.04" leads many people (even some in the federal government) to believe that the legal limit for truckers is 0.04.

To understand why they're wrong, we need to look at other related regulations.

No driver shall -

(1) Use alcohol . . . within 4 hours before going on duty or operating, or having physical control of . . . a commercial motor vehicle;

49 CFR § 392.5(a)

In § 392.5(a)(1), as shown above, the regulations make it very clear that a trucker cannot use alcohol PERIOD within 4 hours before going on duty or in any way physically controlling an 18-wheeler. That rule is another layer added onto the above rule.

So, regardless of whether the trucker has a 0.20 BAC or a 0.00000001 BAC, they cannot use alcohol in the 4-hour window leading up to going on duty or physically controlling a big truck. Thus, the blanket rule of "the legal limit for a trucker is 0.04" is already starting to fall apart.

But you may be thinking, "Well, what if someone drank 5 hours before going on duty, and by the time they go on duty or exercise physical control over a commercial vehicle their BAC has fallen to 0.03? Wouldn't THAT be legal?" After all, they hadn't "used" alcohol within 4 hours and are therefore compliant with § 392.5(a)(1), and they are below a 0.04 BAC and are therefore compliant with § 382.201.

If those were the only two regulations that applied that might be a fair assessment, but there's one other regulation that must also be considered.

No driver shall -

(2) Use alcohol, be under the influence of alcohol, or have any measured alcohol concentration or detected presence of alcohol, while on duty, or operating, or in physical control of a commercial motor vehicle.

49 CFR § 392.5(a)

That regulation does a lot of heavy lifting. It basically says that truckers cannot be under the influence or have ANY measurable amount of alcohol while on duty or while physically controlling a truck in any way. Thus, the blanket rule of "the legal limit for a trucker is 0.04" has taken another huge blow and is starting to look pretty shaky.

Let's go ahead and finish it off.

The first regulation we looked at, 49 CFR § 382.201, mentioned the term "safety sensitive function," as in "no driver can be over 0.04 BAC if they are performing a safety sensitive function (paraphrased)." Some have interpreted that to mean that "safety sensitive function" probably refers to driving, but there are many other things a trucker can do on the clock that aren't safety sensitive.

However, if we look at another regulation—49 C.F.R. §382.107—we see that term safety-sensitive function refers to:

...all time from the time a driver begins to work or is required to be in readiness to work until the time he/she is relieved from work and all responsibility for performing work.

49 C.F.R. §382.107

If we put all these together, we come up with a synthesized rule that makes this complicated issue a lot easier to understand.

The New-And-Improved Synthesized Rule

If a truck driver has a BAC of 0.04 or higher, he can't come to work. And if his employer figures out that he has a BAC of 0.04 or higher, they must send him home.


A trucker can't report for duty or exercise physical control over a commercial vehicle if:

  • They consumed alcohol within 4 hours prior, OR
  • If they are in any way under the influence of alcohol, OR
  • If they have any alcohol in their system.
49 CFR § 382.201, 49 CFR § 392.5(a)(1), & 49 CFR § 392.5(a)(2), simplified.

In short, the legal limit for a truck driver is 0.00, unless you can think of some work-related activity that isn't a safety sensitive function.*

Why Does This Matter?

If you're a truck driver and you're reading this because you got tested for alcohol and think you should be okay since you "only" had a BAC of 0.03, then this matters for the purpose of telling you that you're likely wrong. And you'd better hope that the prosecutor who's handling your case uses the common erroneous belief that the legal limit for truckers is 0.04.

But that's not who we wrote this for.

If instead you're a victim of an accident with a drunk truck driver, this all matters for two reasons. First, you need to know how the law works so you can understand how your case works. Second, you need to understand that not all lawyers are created equal. We have attended seminars and have seen lawsuits filed where lawyers claimed the legal limit for a truck driver is 0.04. This belief is echoed across the trucking and legal industries. As we've demonstrated, however, that's best described as an inaccurate interpretation based on reading only part of the rules.

One of our firm's attorneys is always fond of telling us about how in law school he was given the losing side on several big oral advocacy projects. The idea is that someone gets the short end of the stick and has to argue a case where the law is against them, and their opponent gets the easier side of the case. Well, he never much cared for that arrangement, and so he would dive deeper into the case law, the legislative history, the statutes and regulations, and the legal treatises than any law student before or since. Much to his surprise, in literally every single project, he found that the thought leaders, text books, practice guides, and experts all missed some crucial clue in the law. And in every single instance, he weaponized that discovery against his opponent and came out on top.

Again, not all lawyers are created equal. Some will simply accept the rules on their face and will read a practice guide or the obvious part of a regulation and will accept that 0.04 BAC is the legal limit for a truck driver. Others will make a closer read and form an argument against the conventional wisdom.

We may have a pretty unique perspective on this matter, but some would likely consider that a good thing. Consider this: If you're standing before a judge while your lawyers argue over what allegations to include in a jury charge, do you want a lawyer who meekly concedes that the truck driver that hurt you was technically within the rules because he was "only" a 0.03 BAC, or do you want to be represented by a lawyer who'll say "We think the entire notion of a 0.04 legal limit for truckers is bogus, and here's why we should get to include on the jury charge separate allegations of negligence and negligence per se," thus increasing the odds of winning the case?

If you or a loved one were injured in an accident with a negligent truck driver anywhere in the U.S., the Texas truck accident attorneys at Grossman Law Offices may be able to help. Call today for a free consultation.

*If someone wants to pick nits, there is an agency interpretation that says as a practical matter, only a BAC of .02 counts as a 49 CFR § 382.201 violation. That just means the science isn't there to conclusively prove whether someone who blows under a .02 can reliably be said to have violated the rule. It doesn't change what the law says.

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