Overview

DUI, short for "driving under the influence," describes operating a motor vehicle while impaired by alcohol, illegal drugs, prescription medication, or other substances that reduce a driver's ability to operate safely. The term is widely used in North America; related phrases include DWI (driving while intoxicated), OWI (operating while impaired), and OUI (operating under the influence). Laws, terminology and thresholds vary by jurisdiction, but the core concern is the elevated risk of crashes and fatalities when a driver's faculties are compromised.

Jurisdictions differ in how they define and charge DUI-related offenses. Two common frameworks are "per se" laws, which make it an offense to drive with a blood alcohol concentration (BAC) above a set limit, and impairment standards, which prohibit driving while noticeably impaired regardless of measured BAC. Many countries set BAC limits (often 0.05% in parts of Europe, 0.08% in several North American jurisdictions), and some impose lower or zero-tolerance limits for novice or commercial drivers.

Measurement and testing

Detection combines behavioral observations and chemical tests. Common assessment tools include:

  • Field sobriety tests such as walk-and-turn, one-leg stand, and horizontal gaze nystagmus (HGN).
  • Breath testing using handheld devices or breathalyzers to estimate BAC.
  • Blood and urine tests for precise measurement of alcohol and many drugs.

Drug impairment presents unique challenges because there is no single widely accepted numerical threshold equivalent to BAC for many substances; impairment can depend on drug type, dose, tolerance, and interactions.

Consequences and enforcement

Penalties for DUI range from fines and license suspension to mandatory treatment programs, ignition interlock devices, community service, and imprisonment for serious or repeat offenses. Many places apply administrative actions such as immediate license seizure under implied-consent laws. Law enforcement strategies include sobriety checkpoints, targeted patrols, and specialized DUI courts aimed at reducing recidivism.

History, public health importance, and prevention

Efforts to reduce impaired driving include legal reforms, public awareness campaigns, improved vehicle safety, and technology such as ignition interlocks and ride-hailing alternatives. The introduction of breath-testing devices in the mid-20th century made enforcement more practical; since then, lowering legal BAC limits and expanding penalties have been central to public health strategies. Preventive measures focus on education, designated-driver programs, treatment for substance misuse, and consistent enforcement to reduce injuries and deaths on the road.