Spectral discomfort glare sensitivity under low photopic conditions

Car headlamp manufacturers have to optimise the headlamp spectrum to produce maximum visibility and minimal glare. There are very few investigations on the best spectrum for mesopic visibility and even less data on the spectrum of discomfort glare. We have performed pilot measurements to determine the spectral discomfort glare sensitivity under situations similar to night-driving conditions and conclude that it is not a simple additivity of the V(lambda) and the V' (lambda) functions.