Editing Signal passed at danger (section)

==Etymology==

The name derives from red [[Railway_signal#Colour_light_signals|colour light signals]] and horizontal [[Railway semaphore signal|semaphore signals]] in the United Kingdom, which are said to be ''at danger'' when they indicate that trains must stop (also known as the signal being ''on''). This terminology is not used in North America where not all red signals indicate stop.{{r|cror|p=72}} In the UK, a '''signal passed at red''' ('''SPAR''') is used where a signal changes to red directly in front of a train, due to a fault or emergency, meaning it is impossible to stop before the signal.