20/04/2026
A few days ago we asked you what signal BE158 was part of that was very rare, maybe unique.
The signal is a junction signal for Great Western Junction at the London end of Basingstoke station. It is preceded by flashing yellow aspects for the diverging route towards Reading.
This installation is rare in that, although it has flashing yellows, the junction signal (BE158) has an alphanumeric route indicator, rather than a junction indicator (PLJI). At nearly all flashing junction sequences, the junction signal has a junction indicator ("feather" / five white lights / etc), but this one has an alphanumeric route indicator instead.
Does anyone know the reason? We guess it is to do with sighting, the approaching view being obscured by the station canopy, hence mounting the signal and SARI down so low?
Do you know of any other junction signals preceded by flashing yellows that have an alphanumeric route indicator instead of a junction indicator?
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To address some queries in the comments on the original post: At junctions where flashing yellows are provided the junction signal is normally held at yellow until the train approaches it, and then steps up to a better aspect if it can based on the aspects of the signals ahead.
It wouldn't normally be described as "approach released" without further detail, even though the better aspects are released by the approach of the train, but "approach released" much more conventionally refers to a signal being held at RED until a train approaches it. This is also referred to as "MAR" - Main Aspect approach released from red.
[A flashing junction sequence will fall back to being MAR if the junction signal is not ready to clear by the time the approaching train gets close to the signal that would be flashing yellow. This is to ensure the driver of the approaching train has sufficient time to visually identify and interpret the flashing of the yellow before they pass it.]
A flashing junction sequence is described as "MAY-FA3" or "MAY-FA4" (historically just "MAY") - Main aspect released from yellow with a three or four aspect flashing sequence in rear.
And, for completeness, a junction sequence with no constraints at all - ie where the speeds are the same or almost the same for both routes and the signals show green throughout for both routes - is called "MAF" - Main Aspect Free of restrictions.
