A lighting system for improving the alertness of a person comprising: one or more light sources (101) arranged to emit light into an environment, at least one of the one or more light sources being arranged with a primary function comprising providing illumination into the environment; and a controller (103) configured to cause at least one of the at least one light sources to provide a secondary function of emitting at least a first light pulse (503) having a duration of between 1 ms and 50 ms, wherein there is an idle period (505) lasting at least 0.1 s on either side of the first light pulse.