How do I calculate the critical fall height on a playground?

The critical fall height of impact-attenuating playground surfacing is determined through a series of drop tests in accordance with BS EN 1177. An instrumented headform fitted with an accelerometer is dropped from several heights onto test positions selected on the impact-attenuating surface in accordance with the standard. The critical fall height is the lowest height at which either a HIC value of 1000 is reached or the maximum acceleration, gmax, reaches 200 g; the least favourable test position determines the result.

The result applies only to the tested construction and test conditions. The test report records the surfacing thickness, substrate and relevant test conditions. An on-site test confirms the impact attenuation of the installed surfacing by taking measurements at specified test positions from a prescribed height and checking whether HIC and gmax remain within the limits. The critical fall height is therefore the lowest height at which either the HIC value reaches 1000 or gmax reaches 200 g.