In many states it is a criminal offense (DUI/DWI) to operate a commercial vehicle with a blood alcohol concentration of .04 or more—which is half of the BAC usually required to commit the DUI/DWI offense while driving a non-commercial vehicle. Because most holders of commercial driver’s licenses (CDLs) depend on their license to earn a living, the consequences of a DUI/DWI conviction for a CDL holder—including a conviction while operating a non-commercial vehicle—are serious.

Laws vary from state to state but a CDL holder’s license may be suspended for one year for the first offense, and with a second DUI/DWI conviction the CDL holder may be permanently disqualified from holding a CDL.

These laws are generally located in a state’s statutes—often in the vehicle code, motor vehicle code, or transportation code.

In Alabama, it is indeed a criminal offense for a commercial vehicle operator to have a blood alcohol concentration (BAC) of .04 or more, which is indeed half the BAC limit for non-commercial drivers. For holders of a Commercial Driver's License (CDL), the consequences of a DUI (driving under the influence) conviction can be particularly severe, given their reliance on their license for employment. Under Alabama law, a first DUI offense can result in a one-year suspension of the CDL. If a CDL holder is convicted of a second DUI, they face the possibility of permanent disqualification from holding a CDL. These regulations are typically found in the state's vehicle or transportation codes. It's important for CDL holders to be aware of these stringent standards and the potential impact on their livelihood.