Head Injury Criterion HIC Calculator
Crash biomechanics: Calculate HIC₁₅ and HIC₃₆ from head acceleration pulses, contact duration (t₂ - t₁), and probability of severe traumatic brain injury (AIS ≥ 4).
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Frequently Asked Questions
What is the Head Injury Criterion (HIC) and why is the exponent 2.5?
Developed from the Wayne State University Tolerance Curve and standardized in FMVSS 208, HIC models traumatic brain injury caused by translational deceleration pulses: HIC = (t2 - t1) * [ (1 / (t2 - t1)) * integral a(t) dt ]^2.5. The 2.5 exponent accounts for the severe non-linear damage inflicted on brain tissue as acceleration intensity escalates.
What is the difference between HIC15 and HIC36?
Older safety standards evaluated HIC over any time window up to 36 milliseconds (HIC36 ≤ 1000). Modern crash standards (FMVSS 208 and Euro NCAP) enforce HIC15 (window restricted to Δt ≤ 15 ms, limit ≤ 700). Restricting the window to 15 ms focuses specifically on the dangerous high-g hard-contact phase (such as bottoming out against the steering wheel rim or A-pillar).
What Abbreviated Injury Scale (AIS) levels correlate with HIC scores?
AIS 1 represents minor headache or superficial facial cuts; AIS 2 is moderate concussion with brief unconsciousness; AIS 3 is skull fracture; AIS 4 represents severe unconsciousness (>6 hours) with cerebral contusion; AIS 5 is critical hematoma; and AIS 6 is untreatable fatality. A HIC of 700 corresponds to an approximate 5% risk of AIS ≥ 4, whereas a HIC of 1,500 elevates severe brain trauma risk above 50%.