Photometric Calculations

Controlled reduction of lighting levels is achieved by eliminating first one fixture out of every four, then two fixtures out of four, then three, resulting in a 75% reduction in light levels as the eye adapts to the lower levels of the tunnel interior.  One of the quirky issues that only really come up in tunnel lighting is that the spacing of the fixtures must be done in such a way that the lights will not appear to strobe as motorists flash by them, which would distract the drivers.