"Drunk driving" is a fairly well-defined criminal offense in all 50 states. There are generally two crimes set forth by statute: (1) driving a vehicle under the influence of alcohol and (2) driving a vehicle with a blood-alcohol content of .08% or higher. The only differences are in relatively minor variations as to what a "vehicle" is and what constitutes being "under the influence".
In marked contrast, however, the definitions of driving under the influence of drugs (so-called "drugged driving" or "DUI drugs") vary significantly from state to state. In one state, for example, the crime consists of driving while "impaired by" or "under the influence of" a drug. In another, it may be defined as driving with a specifically designated amount of the drug in the blood. In yet another, the offense is committed if there is any measurable amount of the drug in the body — and in some states this will include marijuana, while in others it does not.
Do you know what the drugged driving laws are in your state?
Fortunately, the National Alliance for Model State Drug Laws (NAMSDL) in Charlottesville, Virginia, supported by grant from the U.S. Office of National Drug Control Policy, has provided a chart entitled State Drugged Driving Standards which readily identifies the laws of each state.