Transitions is a human centric lighting design concept for Melbourne’s underground metro. It incorporates a dynamic circadian lighting system where the colour temperature of the luminous environment gradually transitions throughout the day to provide users of the space with appropriate lighting for the body’s circadian rhythms. Circadian rhythms are physiological rhythms within the body that follow a pattern of variation over a period. The timing of circadian rhythms is regulated by the onset and suppression of melatonin production triggered by light entering the retina. Inappropriate lighting can lead to health problems when circadian rhythms become out of phase with the environment.