Basic tests on actively illuminated visibility clothing

Status:

completed

Aims:

The type of high-visibility clothing equipped with retroreflective sections that has been used to date is not clearly visible when used in work areas where no external light source is present. As a result, retroreflective sections on high-visibility clothing do not ensure that the person wearing the clothing can be seen.

The aim of this project was to incorporate the findings from basic tests into the DIN SPEC pre-standard 91418 "Warning clothing with active lighting in addition to DIN EN ISO 20471 and DIN EN 1150 — Requirements and test methods". In the future, this specification is intended to enable a uniform approach to self-illuminating high-visibility clothing (warning clothing with active lighting) and define minimum visibility requirements. This DIN SPEC defines basic requirements in order to standardise – and therefore simplify – the development of self-illuminating high-visibility clothing (warning clothing with active lighting) for manufacturing companies. Furthermore, the results are to be used to aid the development of the new testing laboratory for self-illuminating high-visibility clothing (warning clothing with active lighting).

Activities/Methods:

To carry out the investigations, various light sources such as LEDs, LED tape lights and fibre optic lighting in a wide range of designs and colours were used, as well as a suitable measuring technology for assessing the components in terms of their luminance at various beam angles. In addition, the study also aimed to clarify which light sources are capable of ensuring the visibility of the wearer throughout the entire service life of the high-visibility clothing. The position of the light source on the high-visibility clothing plays a crucial role in ensuring 360° visibility of the wearer. The initial tests were performed on high-visibility vests. The aim of these tests assessing suitable positioning of the light source on high-visibility vests was to determine the best positions for light sources on high-visibility clothing.

The planned budget was used to create a measurement set-up with a rotating plate (360° visibility) and a camera measurement system (luminance).

Additional aspects were also investigated, such as electromagnetic compatibility (EMC), electromagnetic fields (EMF) for individuals with implants, electrical safety, IP protection classes, mechanical requirements, battery safety and also questions relating to the cleaning/washing of self-illuminating high-visibility clothing (warning clothing with active lighting).

Results:

Market research showed that almost all self-illuminating high-visibility clothing (warning clothing with active lighting) that is currently available on the market is equipped with individual LEDs or LED arrays. Nevertheless, the results and derived requirements were described in a way that ensures that they can be applied to all technologies and that they can be incorporated into standards. One of the most important key values is the visibility of the product at a defined distance. In order to define this key value, tests were carried out with test subjects in the dark. During this series of tests, the test subjects (n=32) had to make a statement about how well they were able to see a test specimen at various distances (50 m, 100 m and 150 m) or whether they were able to see it at all. The test specimens used included self-illuminating high-visibility clothing (warning clothing with active lighting) that is presently available as well as self-built test specimens with LED arrays of different sizes and with different distances between the LEDs. During the series of tests, the luminance of the test specimens was also adjusted in order to determine a minimum and maximum limit value for visibility and glare. During the series of tests, it was determined that individual LEDs at a minimum distance of 10 cm from each other and smaller LED arrays up to 4 cm² in size are already difficult to see at a distance of 50 m with a luminance of 10 cd/m². When testing a wide range of lighting set-ups, the best results were achieved with luminance values of around 400 cd/m². The results from this project have been incorporated into DIN/TS 91418, which was published in July 2021. The results of the series of tests were incorporated directly into the specification as a table in Annex B . Manufacturers are now required to provide information about the visibility of the product based on this table and to comply with a maximum limit value for luminance in order to avoid glare/dazzling. The recently published specification also defines requirements for electrical safety, IP protection classes and EMC/EMF, and stipulates that 360° visibility must be ensured when self-illuminating high-visibility clothing (warning clothing with active lighting) is used. There is no standard requirement for the arrangement of the light sources on the high-visibility clothing, as the requirement for 360° visibility is sufficient in this context. For specifications relating to electrical safety, IP protective classes and EMC/EMF, the Institute for Occupational Safety and Health of the German Social Accident Insurance (IFA) was able to draw on previous experience and existing requirements and incorporate these into the standard.

In order to ensure reproducible measurement of the luminance for self-illuminating high-visibility clothing (warning clothing with active lighting), the follow-up project IFA 5159 (Establishment of a "photometric laboratory") was initiated.

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