Luminance and pedestrians' perceived ability to see after dark: Mapping the Netherlands using a citizen science network of smartphone users

We studied pedestrians' perception of their ability to see when outside after dark, the luminance of the pavement after dark and the association between perception and luminance. These data were captured by a citizen science network of smartphone users, with and without an eye disease. They used an app to report their ability to see when outside after dark in their own neighbourhood and measured the luminance of the pavement using the smartphone camera. Logistic regression was used to determine the influence of luminance, age, gender and eye disease on reported ability to see after dark. Amongst those respondents who did not report an eye disease, 11% reported visual conditions they perceived to make walking difficult; this increased to 40% for pedestrians who reported an eye disease. The recorded luminances were typically 0.01-0.1 cd/m(2). For those respondents with healthy eyes, the percentage reporting difficult visual conditions increased especially below 0.01 cd/m(2); for those with an eye disease, the increase started at higher luminances, which may limit their mobility after dark.