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Aspect
The colour of a signal lamp or combination of lamps on one signal is known as the aspect. The signal aspect provides an unambiguous message to the driver of a train. The signal lamp can also be made up of LEDs as this is now perceived to give the driver a clearer display of the aspect, especially when bright sunlight is shining onto a signal. In the UK, and simulated on SimSig there are three and four aspect signalling areas.
3 Aspect signals
The normal sequence of three aspect signalling is:
| Green aspect | Proceed | Next signal displaying a proceed or caution aspect |
| Yellow aspect | Caution | Proceed but be prepared to stop at the next signal |
| Red aspect | Danger | STOP! |
4 Aspect signals
The normal sequence of four aspect signalling is:
| Green aspect | Proceed | Next signal displaying a proceed or preliminary caution aspect |
| Two yellow aspects | Preliminary caution | Proceed but be prepared to find the next signal showing one yellow aspect |
| Yellow aspect | Caution | Be prepared to stop at the next signal |
| Red aspect | Danger: | STOP! |
Comparison
 |
4 aspect signals 3 aspect signals |
Flashing Yellows
In addition to the above on certain junctions is ‘Flashing Yellow Signalling’ this indicates that the facing points ahead are set for a diverging route, over which the speed of the train must be reduced. These are present in both three and four aspect signalling areas.
The normal sequence of three aspect flashing yellow signalling is:
- Green aspect
- Green aspect
- Single flashing yellow aspect
- Steady single yellow aspect with a junction indicator (the latter not shown to the signaller or on SimSig)
- Red aspect
The normal sequence of four aspect flashing yellow signalling is:
- Green aspect
- Double flashing yellow aspect
- Single flashing yellow aspect
- Steady single yellow aspect with a junction indicator (the latter not shown to the signaller or on SimSig)
- Red aspect
If there is a route set from the red aspect (5) upon approach the steady single aspect (4) will clear to the relevant aspect as described above in three and four aspect signalling.
Last edited by GeoffM on 15/09/2016 at 03:01