An accident is an unintended, normally unwanted event that was not directly caused by humans. The term accident implies that nobody should be blamed, but the event may have been caused by unrecognized or unaddressed risks. Most researchers who study unintentional injury avoid using the term accident and focus on factors that increase risk of severe injury and that reduce injury incidence and severity. For example, when a tree falls down during a wind storm, its fall may not have been caused by humans, but the tree's type, size, health, location, or improper maintenance may have contributed to the result. Most car wrecks are not true accidents; however English speakers started using that word in the mid-20th century as a result of media manipulation by the US automobile industry.
Physical examples of accidents include unintended motor vehicle collisions, falls, being injured by touching something sharp or hot, or bumping into something while walking.
Non-physical examples are unintentionally revealing a secret or otherwise saying something incorrectly, accidental deletion of data, or forgetting an appointment.
Vehicle collisions are not usually accidents; they are mostly caused by preventable causes such as drunk driving and intentionally driving too fast. The use of the word accident to describe car wrecks was promoted by the US National Automobile Chamber of Commerce in the middle of the 20th century, as a way to make vehicle-related deaths and injuries seem like an unavoidable matter of fate, rather than a problem that could be addressed. The automobile industry accomplished this by writing customized articles as a free service for newspapers that used the industry's preferred language. Since 1994, the US National Highway Traffic Safety Administration has asked media and the public to not use the word accident to describe vehicle collisions.
In the process industry, a primary accident may propagate to nearby units, resulting in a chain of accidents, which is called domino effect accident.
See also: Preventable causes of death
Poisons, vehicle collisions and falls are the most common causes of fatal injuries. According to a 2005 survey of injuries sustained at home, which used data from the National Vital Statistics System of the United States National Center for Health Statistics, falls, poisoning, and fire/burn injuries are the most common causes of death.
The United States also collects statistically valid injury data (sampled from 100 hospitals) through the National Electronic Injury Surveillance System administered by the Consumer Product Safety Commission. This program was revised in 2000 to include all injuries rather than just injuries involving products. Data on emergency department visits is also collected through the National Health Interview Survey. In The U.S. the Bureau of Labor Statistics has available on their website extensive statistics on workplace accidents.
Many models to characterize and analyze accidents have been proposed, which can be classified by type. No single model is the sole correct approach. Notable types and models include:
Ishikawa diagrams are sometimes used to illustrate root-cause analysis and five whys discussions.
Since 'accidents' by definition deprive us of first-order human causes…