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None of my fellow commuters know what this white panel with, what appears to be a red slider attached, is called and what it is for.

This particular one is on a platform edge which happens to be over a bridge (Maidenhead in Berkshire).

Does anyone know? The track is a straight section at this point. So I don't think it's any indication of cant.

enter image description here

Bathsheba
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1 Answers1

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Google has the answer (second result):

  • They mark the height of the nearest rail.
  • Height with respect to the little slider thing, so the track position is usually an amount below the indicator. They are also found on some pieces of trackside equipment such as OHLE or signal gantries - but they aren't so readily seen, so mostly go without comment. Anywhere where the track position cannot vary too much away from the 'as installed' position basically.
  • There are datum plates, when track is relaid or worked on it allows measurement to ensure the vehicle clearance is maintained

So basically it's there to mark what height the rail should be installed to, presumably in your case to ensure sufficient clearance to the bridge above.

AndyT
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  • Very many thanks for this! (The platform is actually the bridge span - the road passes under. My guess therefore is that it's there to maintain a good height w.r.t. the platform.) – Bathsheba Feb 28 '17 at 17:45