Analytical Studies of the Head Injury Criterion (HIC)

The Head Injury Criterion (HIC) in FMVSS 208 for evaluating the potential head injury requires maximization of a mathematical expression, involving the time-average acceleration, by varying the limits (t sub 1, t sub 2) of the time interval over which the average is calculated. This paper describes the HIC behavior through the analysis of a function of two independent variables t sub 1 and t sub 2. The analysis is carried out for any arbitrary acceleration profile a(t). It is found that maximization requires that a(t sub 1) = a(t sub 2). Also, for the unique values of t sub 1 and t sub 2 that maximize HIC, the average acceleration between t sub 1 and t sub 2 is 5/3 times the acceleration at t sub 1 or t sub 2.