If signals 9, 10, 11 and 12 are red then signal D will be red. If signals 5, 6, 7 and 8 are red then signal B will be red. If signals 1, 2, 3 and 4 are red then signal A will be red. The signal E is the only Pre-signal (Entrance) Signals 1 through 12 are Pre-signal Exits 3 - An "optimal" RoRo station layout with presignals. Y turns red for northbound trains, and Y is an exit signal for X, so X turns red, which is an exit signal for AB which also turns red.įig.
Here it is the other way around: A southbound train enters the single track at CD. In the meantime, an east-west train can pass through. Y is an exit signal for CD, so they both turn red for southbound trains too. X is an exit signal for Y, so Y also turns red for southbound trains. A northbound train enters the single track at AB. How it works: Call the southern entrance signals AB, the combo signals at the intersection X (south side) and Y (north side), and the northern entrance signals CD. (You can keep using normal two-way signals for the east-west line.) At the intersection, set up combo pre-signals (vertical yellow) on the north-south line. Set up entrance pre-signals (horizontal yellow) where the trains on the north-south line switch onto the single track. The problem: the signals break up the north-south section of track, meaning a northbound train could meet a southbound train at a red light at the intersection. You run the tracks across each other, and make a 4-way intersection surrounded by regular two-way signals.
It can't wait for northbound and southbound trains to clear the whole single section. What if you want a new east-west track to cross the north-south track? Let's say you don't want to use a bridge, and your new east-west track is a high-speed service. You'd use regular two-way signals where the lines switch onto the single section (four in total, one for each switch). This example should give you a good idea of the help that pre-signals can be, and an example of combo signals.įor example, a line has two trains, each going to its own station.Both trains travel along a single north-south track for part of the way. Pre-signals and a single track intersection 1 Pre-signals and a single track intersection.
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