Driving While Impaired (DWI) occurs where a person drives a motor vehicle upon any highway, street, or public vehicular area at a time when the person was either under the influence of an impairing substance, which means the person had taken or consumed a sufficient quantity of the substance to cause the person to lose the normal control of their bodily or mental faculties, or both, to such an extent that there is an appreciable impairment (impairment is deemed appreciable when it is sufficient to be recognized and estimated) of either or both of these faculties, had consumed a sufficient quantity of alcohol that the person had an alcohol concentration of 0.08 (which is determined by a breath sample that is analyzed by an Intoxylizer machine) or more grams of alcohol per 210 liters of breath or per 100 milliliters of blood (which is determined by a blood test), or had any amount of a Schedule I Controlled Substance, or metabolites of a Schedule I Controlled Substance, in their blood or urine; a metabolite is any substance produced or used during metabolism and refers to the end product that remains after the drug has been metabolized.

For purposes of DWI, a motor vehicle is defined as either any vehicle that is self-propelled, any vehicle designed to run upon a street or highway that is pulled by a self-propelled vehicle, a moped (which is defined as a vehicle that has two or three wheels, no external shifting device, and a motor that does not exceed 50 cubic centimeters piston displacement and cannot propel the vehicle at a speed greater than 30 miles per hour on a level surface) or a bicycle.