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:
“People who are not in love fail to understand how an intelligent man can suffer because of a very ordinary woman. This is like being surprised that anyone should be stricken with cholera because of a creature so insignificant as the common bacillus.”
—Marcel Proust (1871–1922)
“She would refuse love safe with wealth and honor!
The lovely shall be choosers, shall they?
Then let them choose!’”
—Robert Frost (1874–1963)