Head injury criterion

The Head Injury Criterion (HIC) is a measure of the likelihood of head injury arising from an impact. The HIC can be used to assess safety related to vehicles, personal protective gear, and sport equipment.

Normally the variable is derived from the measurements of an accelerometer mounted at the centre of gravity of a crash test dummy’s head, when the dummy is exposed to crash forces.

It is defined as: ${\mathit {H}}{\mathit {I}}{\mathit {C}}={\bigg \{}{\Big [}{\frac {1}{t_{2}-t_{1}}}\int _{t_{1}}^{t_{2}}a(t)dt{\Big ]}^{2.5}\left(t_{2}-t_{1}\right){\bigg \}}_{max}$ $\mathit{H}\mathit{I}\mathit{C} = \bigg\{ \Big[ \frac{1}{t_{2}-t_{1}} \int_{t_{1}}^{t_{2}} a(t) dt\Big]^{2.5}\left ( t_{2}-t_{1}\right ) \bigg\}_{max}$

where t₁ and t₂ are the initial and final times (in seconds) of the interval during which HIC attains a maximum value, and acceleration a is measured in gs (standard gravity acceleration). The maximum time duration of HIC, t₂ – t₁, is limited to a specific value between 3 and 36 ms, usually 15 ms.

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