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 Connecticut, the operation of a commercial vehicle with a blood alcohol concentration (BAC) of .04 or higher constitutes a criminal offense, which is a lower threshold than the .08 BAC typically required for a DUI/DWI offense in a non-commercial vehicle. For holders of a commercial driver's license (CDL), the stakes are particularly high as their livelihood often depends on maintaining a valid CDL. Under Connecticut law, a first-time DUI/DWI offense can result in a one-year suspension of the CDL. If a CDL holder is convicted of a second DUI/DWI, they face the possibility of being permanently disqualified from holding a CDL. These regulations are designed to promote safety on the roads and ensure that commercial drivers adhere to stricter standards given the potential consequences of impaired driving in larger vehicles. The relevant laws can be found in the state's statutes, specifically within sections related to motor vehicles or transportation.