QUOTE (Colombo @ 22 Feb 2009, 17:47) <{POST_SNAPBACK}>Also PLGS are often mounted on gantries or on signal posts with the red blanked off. In this case they only display proceed at caution to the next stop signal. the red lense on the main signal display indicates stop, of course.
Sorry not quite true. Yellow on the main aspect indicates proceed at caution to the next stop signal or to a buffer stop. Two white lights alongside or below a main red aspect is known as a subsidiary aspect and indicates proceed at a safe speed to stop short of any obstruction that comes into view. This includes another train standing in a plaform or a position light ground signal showing a danger aspect. The subsidiary aspect is only illuminated as the train closely approaches it, to ensure that it has been slowed down.
If a main route (yellow, double yellow or green) is set to pass a position light ground signal then the latter will always be "preset" to show two white lights so as to avoid the driver seeing a red aspect.
Sorry not quite true. Yellow on the main aspect indicates proceed at caution to the next stop signal or to a buffer stop. Two white lights alongside or below a main red aspect is known as a subsidiary aspect and indicates proceed at a safe speed to stop short of any obstruction that comes into view. This includes another train standing in a plaform or a position light ground signal showing a danger aspect. The subsidiary aspect is only illuminated as the train closely approaches it, to ensure that it has been slowed down.
If a main route (yellow, double yellow or green) is set to pass a position light ground signal then the latter will always be "preset" to show two white lights so as to avoid the driver seeing a red aspect.
