How is the critical fall height determined in accordance with BS EN 1177?

The critical fall height of impact-absorbing surfacing is established through a series of drop tests to BS EN 1177. A test head fitted with an accelerometer is dropped from several heights onto test locations selected in accordance with the standard. The critical fall height is the lowest height at which either HIC reaches 1000 or gmax reaches 200 g. The result is governed by the least favourable location tested.

The test result applies only to the surfacing construction and conditions assessed. The test report records, among other details, the surfacing thickness, substrate and relevant test conditions. For installed impact-absorbing surfacing, an on-site test can confirm impact attenuation. Measurements are taken at specified locations from a prescribed height to establish whether HIC and gmax remain within the limit values.