In every state, it’s illegal to drive a vehicle while under the influence of drugs or alcohol. However, states use lots of different names to describe impaired driving. These names include:
Each state has its own naming convention, but DUI and DWI are the most common and are often used even when the official name for driving under the influence is something different.
Despite all the different names, state DUI laws are fairly similar in how they define drunk and drugged driving. So, for the most part, the names don’t matter all that much.
In every state, a person can be convicted of a DUI based on blood alcohol concentration (BAC) or actual intoxication. A DUI that's based on BAC is often called a “per se DUI.” With the exception of Utah (where the maximum BAC level is more strict), all states define per se DUI as operating a vehicle with a BAC of .08% or more. Some states like Washington and Indiana also have per se drug-DUI laws that make it illegal to drive with a certain concentration of drugs in your system.
All states have impairment DUI laws. But the laws of each state define the prohibited level of impairment differently. For example, in California, a person is considered to be under the influence if “substantially” affected by drugs or alcohol. Nebraska DUI law, on the other hand, defines under the influence as having your ability to safely operate a vehicle impaired to any “appreciable degree.”
Many states use several names to describe different classes of impaired driving offenses. For instance, the standard drunk or drugged driving offense in New York is called “driving while intoxicated” or “DWI.” But New York also has a less serious offense called “driving while ability impaired” or “DWAI.”
Generally, when a state has two types of impaired driving offenses, the distinction between the two is based on the driver’s level of impairment. For example, a person can be convicted of a DUI in Colorado for operating a vehicle while substantially impaired and the less serious offense, DWAI, for driving while slightly impaired.
In states that have multiple impaired driving classifications, a defendant who’s charged with driving under the influence can sometimes plea bargain for the lesser impaired driving offense.