Visibility of protective helmets worn by forestry workers.
BACKGROUND: High visibility helmets must be worn by forestry workers in New Zealand for protection and as conspicuous 'clothing' to alert workers to the presence and location of other workers. The colours yellow-green (fluorescent yellow-green) and 'watermelon' (fluorescent pink) are used and both appear to be conspicuous. To solve a controversy, we investigated which helmet colour is more visible for use in a forest setting for workers having normal or defective colour vision. METHOD: We obtained threshold angular sizes for two-millimetre square samples of helmet material presented against a textured background containing colours representative of those found in the foliage and bark of the most common forest type (Pinus Radiata). Observers with normal colour vision (n = 22) and with deutan (n = 8) and protan (n = 6) defects participated. Subjects with mild colour vision defects were excluded. RESULTS: The yellow-green colour was significantly more visible than the pink for the normal (p +/- 0.001) and protan (p +/- 0.05) observers. For the deutan observers the pink helmet colour was significantly more visible (p +/- 0.01). The median equivalent outdoor detection distances were for normal observers 400 m (pink) and 500 m (yellow-green); for protan observers 185 m (pink) and 500 m (yellow-green); and for deutan observers 550 m (pink) and 450 m (yellow-green). CONCLUSIONS: The yellow-green helmet can be detected at large distances by all observers. The yellow-green helmet has greater reflectance and therefore greater luminance contrast. The pink helmet colour can be confused with green forest background colours by observers with protan defects. For some observers with a protan colour vision defect, detection distances for the pink helmet colour are less than half of normal detection distances.
Jacobs
Robert J
RJ
Department of Optometry and Visual Science, The University of Auckland, Private Bag 92019, Auckland, New Zealand.
De Bock
Jelle
J
Chouhan
Jayesh
J