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 Iowa, it is indeed a criminal offense for a commercial vehicle operator to have a blood alcohol concentration (BAC) of .04 or higher, which is in line with federal regulations. This limit is stricter than the .08 BAC limit for non-commercial drivers. For holders of a Commercial Driver's License (CDL), the consequences of a DUI/DWI are particularly severe. If a CDL holder is convicted of a DUI/DWI for the first time, they face a one-year suspension of their CDL. If they are convicted of a second DUI/DWI, they may be permanently disqualified from holding a CDL. These regulations are designed to ensure the safety of the roads and to hold commercial drivers to a higher standard due to the potential for greater harm in commercial vehicle accidents. The specific laws governing DUI/DWI offenses for CDL holders in Iowa can be found in the state's transportation code.