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)
“The almost unexplored Everglades lay close by and with a half- hour’s start a man who knew the country was safe from pursuit. As one man cheerfully confided ..., ‘A boat don’t leave no trail, stranger.’”
—For the State of Florida, U.S. public relief program (1935-1943)