Fail Safe
Because the aspects are in reverse with more green lights meaning slower the aspects are not fail safe, so lamp proving is needed to prevent lamp failure giving a faster aspect.
Single and Double Green signals work the other way with Norwegian railway signalling and it would be unsafe for drivers to cross the border, unless ATP were fitted.
Read more about this topic: Swedish Railway Signalling
Famous quotes containing the words fail and/or safe:
“There is a mortifying experience in particular, which does not fail to wreak itself also in the general history; I mean “the foolish face of praise,” the forced smile which we put on in company where we do not feel at ease, in answer to conversation which does not interest us. The muscles, not spontaneously moved but moved, by a low usurping wilfulness, grow tight about the outline of the face, with the most disagreeable sensation.”
—Ralph Waldo Emerson (1803–1882)
“Fences, unlike punishments, clearly mark out the perimeters of any specified territory. Young children learn where it is permissible to play, because their backyard fence plainly outlines the safe area. They learn about the invisible fence that surrounds the stove, and that Grandma has an invisible barrier around her cabinet of antique teacups.”
—Jeanne Elium (20th century)