Motor vehicle traffic accidents can be studied by the events they contain, often by the harmful events. The first harmful event of an accident refers to the first injury or damaging producing event that occurs. The most harmful event is typically recorded for each involved unit. It refers to the event that produces the most severe injury or amount of damage for each unit. Sequence of Events is entered in SAFETYNET for qualifying vehicles. It records both collision and non-collision events time-wise as they occurred in the accident up to a total of four events. For accidents with more than four events in the sequence, it is suggested to omit the event(s) least relevant to describing the crash.