Killed or Seriously Injured

Killed or Seriously Injured (KSI) is a standard metric for safety policy, particularly in transportation and road safety.

The definitions used in the USA are as follows:

Figures for fatalities are normally highly reliable in industrialised countries and few if any fatalities go unrecorded. Fatality figures are however often too low making it hard to see trends over time for one place.

Figures for the number of people seriously injured typically being an order of magnitude larger than the number of people killed and are therefore more likely to be statistically significant. However, classification of serious injuries is open to opinion, by medical staff or by non-medical professionals, such as police officers and may therefore vary over time and between places.

Figures for slight injuries are considered highly unreliable, largely due to under-reporting where injuries are self-treated.

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