DUI or Driving Under the Influence (sometimes called DWI or Driving While Intoxicated) is a criminal offense in most states (most countries, actually). The substance can be alcohol or drugs, which is why it's not merely called "drunk driving" anymore.
DUI citations naturally are of grave concern to fleet managers, whose drivers endanger the company if caught driving impaired.
For more information on this important safety topic, search for articles with the keywords DWI, DUI, and the increasingly deadly distracted driving.
How Fleets Handle DUI Cited Drivers
Identifying High Risk Drivers