We defined Collision Impact Index (CII) of each part of human body due to falling down. The formula of CII is defined similar to HIC. The meaning is "Powered averaged acceleration and the time product". In order to make clear the usefulness of the Index CII, the experiment was done in JARI, and the acceleration data are taken on the head, chest and pelvis of a dummy robot, which simulates the human body. The acceleration data was measured in the step of 0.0001 second, and analyzed on the basis of the proposed formula of CII. As a result, it is shown that index CII is reasonable because (1) the ratios are similar dependence in spite of the power, (2) only peak is selected by the power, (3) the selected time intervals are almost constant, although the width becomes narrow as the power goes large.
