What does "driving under the influence" (DUI) mean?

"Driving under the influence" (DUI) specifically refers to the act of operating a motor vehicle while impaired by substances, which can include alcohol, illegal drugs, or even certain prescription medications. This definition is crucial because it highlights the impairment aspect that affects a driver's ability to operate a vehicle safely. Impairment can lead to slower reaction times, reduced coordination, and an overall increased risk of accidents.

Option B accurately captures the essence of DUI laws and their enforcement, which are designed to prevent dangerous driving behaviors that result from substance use. This notion is grounded in public safety, as driving under the influence poses significant risks not only to the impaired driver but also to other road users.

Options such as driving while drowsy or tired, driving without a valid license, and exceeding the speed limit do not encompass the specific legal implications and safety concerns associated with being under the influence of substances. These behaviors, while potentially dangerous, do not fall under the legal definition of DUI, which is focused on impairment due to substances.