Driving under the influence

Driving under the influence is the offense of operating a vehicle while impaired by alcohol, drugs, or another intoxicating substance. Laws define impairment and prohibited conduct differently across jurisdictions.

Blood alcohol concentration: The proportion of alcohol in a person's blood, commonly expressed as grams per deciliter or a percentage. Many jurisdictions use a specified concentration as a per se threshold for alcohol-related offenses.
License suspension: A temporary withdrawal of a person's legal privilege to drive. An arrest, test result, or conviction may trigger suspension independently of other penalties.
Reckless driving: Driving with willful or wanton disregard for the safety of people or property, as defined by law. Reckless driving concerns dangerous conduct, while this offense centers on impairment or prohibited substance levels.
Sobriety checkpoint: A law-enforcement operation that stops vehicles according to a systematic plan to check for driver impairment. Checkpoint policies seek to increase detection and deterrence while meeting constitutional and statutory limits.
Field sobriety tests: Standardized roadside tasks used to assess signs of impairment, including balance, coordination, and attention. Officers may use these observations to develop grounds for further testing or arrest.
Ignition interlock device: A vehicle-installed breath-testing device that prevents operation when alcohol is detected above a set level. Courts or licensing agencies may require one before driving privileges are restored.
Open-container law: A law restricting possession of opened alcoholic beverages in vehicle passenger areas. An open container may be evidence or a separate violation, but does not by itself prove impaired driving.
Designated driver: A person who abstains from alcohol so they can safely drive others after a social event. Planning a sober ride is a direct prevention strategy for alcohol-impaired driving.
Breathalyzer: A device that estimates or measures alcohol concentration from a person's breath. Breath testing can provide evidence of alcohol concentration after a traffic stop.
DUI checkpoint: A roadblock where law enforcement briefly stops vehicles to identify impaired drivers under applicable rules. Checkpoints are one enforcement approach intended to deter and detect impaired driving.

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