The impact-attenuating properties are determined in a special test procedure with the determination of the so-called HIC value in accordance with the standard DIN EN 1177:2024 (Impact-attenuating playground surfacing – Test method for determining the impact attenuation, German version EN 1177:2024). ‘HIC’ stands for ‘Head Injury Criterion’ – a value used in technical studies to estimate the risk of serious head injuries resulting from an impact after acceleration. It plays an important role, for example, in safety tests for motor vehicles (see ‘crash tests’), but also in the requirements for safety surfacing in playgrounds.

The higher the HIC value in the event of an impact, the higher the risk that the person who has fallen will suffer a serious head injury as a result. The HIC value of 1000 is defined as the limit value for playground surfacing tests. The height at which this value is undercut for the last time in the test is also the maximum permissible fall height, which is determined by means of certain test procedures in which an impact with the head on the respective safety surfacing is technically simulated. In addition to the HIC value, there is also the so-called ‘gmax’ value, which was also added as an independent parameter during the last revision of the standard. The ‘g’ here physically stands for ‘gravity’ and indicates the acceleration at the moment of impact. Although this value is already included in the calculation of the HIC value, it also has to be taken into account separately in measurements since the standard was last revised. This value has a limit of 200. The two limit values help to ensure that the risk of serious head injuries is minimised in the event of a fall from the relevant height onto the tested safety surfacing – however, an injury cannot be completely avoided. Nevertheless, the risk can be well estimated and minimised.

If, after successful testing, a safety surfacing is suitable for a certain fall height, it is important that this result is properly documented afterwards. The basis for every suitability assessment should therefore be a test report from an ISO 17025 accredited testing institute or laboratory, as this ensures qualification, verification and comparability.

In accordance with the strict requirements of standard DIN EN 1177, such a test report must contain the following information:

1. A number and the date of issue of this European Standard, i.e. EN 1177:2024;
2. A complete description of the tested product;
3. A photograph of the tested material with an indication of the scale in the case of loose bulk materials;
4. The method by which the test specimens are kept together or the internal dimensions of the test container and the tested layer thickness for loose bulk material;
5. A diagram showing all test positions;
6. The properties of the floor at the time of the test (e.g. temperature and humidity);
7. The results of each drop test, indicating the drop heights applied and the corresponding HIC values and gmax values;
8. The critical drop height of the tested floor, given in metres to two decimal places;
9. The curves of the HIC value and gmax value versus the drop height, which were used to determine the critical drop height of the floor;
10. A time/acceleration curve of an impact with HIC value or gmax value.

The second method describes an on-site drop test that provides the necessary confirmation of the suitability of the ground for the specific location (with the specified free fall height of the installed play equipment) at the time of the test. The usability of the safety surfacing is therefore tested directly in its installed condition. However, the technical implementation basically corresponds to the first method, just not under ‘laboratory conditions’.

In this case, however, a specific fall height is not determined, but rather it is tested whether the safety surfacing is suitable for a fall from a previously defined height. This is determined either by the height of an existing play equipment or by the height of a play equipment intended for later installation. The procedure then shows whether the impact-attenuating properties of the surface already installed, in conjunction with the existing or planned play equipment, meet the requirements of the standard.

It is usually applied to check the suitability of the installed surfacing again after the construction of the playground or when a new installation of play equipment is planned on existing surfacing.

It should, of course, always be noted that the relevant standard is regularly revised and republished. Test reports used to verify the suitability of the safety surfacing system should therefore always comply with the current issue date of the EN 1177 standard. It is recommended to repeat the testing of the safety surfacing material after about three years.