Gawd. If I remember correctly that "ALL" means both "RLU" and "FLU" ? (Class 700 8-car Reduced Length Units and Class 700 12-car Full Length Units respectively). Now we had to add "717" as in class 717. One day we might simplify the stop signs to just say things like 6 car, 8 car and 12 car etc
. I know coaches nowadays can be different lengths but surely something more logical can be thought of rather than this "evolution". At least in this case surely this is the stop point for ANY length train - or are 387s and 365s expected to stop somewhere different ?.
I get the purpose of the RLU / FLU signs is to ensure the CENTRE of any length class 700, where the disabled loo is, stops in exactly the same place for the raised bit of the platforms. Is there similar for the 717s btw ? - no disabled loo to worry about of course.
There are some stations with 387 stop markers. These are located for signal sighting (387 has a particularly poor view on the right hand side).
Original style 3, 4, 6, 8, 12, and S car markers are for 313s, 365s, and 387s where there isn't a separate 387 marker. You stop with the front of the train level with the marker.
387 markers you stop with in your small left hand window if they are on the left, or lined up in view with the right hand edge or bottom edge of the windscreen if they are on the right or in the four foot.
RLU, FLU, or ALL are lined up in view with the edge of the windscreen on 700s and signal sighting is taken into account, making some stations SDO (like Tulse Hill on Thameslink being 6 1/2cars compared to 8 cars for Southern).
Also the disabled access is a factor for 700s as well.
717s have their own marker, they are 6 car trains, but again signal sighting particularly on the right hand side has led to the proposed arrangement to the NCL stations (right hand side signals on most platforms) having the stopping point more forward than previously, and SDO for the front five coaches only.
It seems that unlike the, "which board am I using at this station, with this train length?" inconsistency with class 387s, the 717s have been given boards at all stations, like the 700s have.