Drunk driving is the act of operating or driving a motor vehicle while under the influence of alcohol or drugs to the degree that mental and motor skills are impaired. It is illegal in all jurisdictions within the United States, though enforcement varies widely between and within states/territories. The specific criminal offense is usually called driving under the influence (DUI), and in some states 'driving while intoxicated' (DWI), 'operating while impaired' (OWI), or 'operating a vehicle under the influence' (OVI). Such laws may also apply to boating or piloting aircraft. Vehicles can include farm machinery and horse-drawn carriages. In the United States the National Highway Traffic Safety Administration (NHTSA) estimates that 17,941 people died in 2006 in alcohol-related collisions, representing 40% of total traffic deaths in the US. NHTSA states 275,000 were injured in alcohol-related accidents in 2003.