Help please with sign

[eMeS]

I took some snaps a year ago of the Talerddig Cutting, and found that I'd included this sign a short distance from the road bridge.
I've done a search, but so far haven't found any info. Many thanks.

 

[4F89]

ERTMS (European Rail Traffic Management System) block markers.

 

[Domh245]

ERTMS block marker (see 12.33 on this page) - in essence the physical marker of where a 'virtual' signal is for lines signalled with ERTMS (of which the Cambrian is one)

 

[eMeS]

Thank you both.

 

[hexagon789]

Is there any difference between the triangle-shaped ones (which seem to be the norm on HS1 and French LGVs) and these 'arrow'-shaped ones?

 

[edwin_m]

Is there any difference between the triangle-shaped ones (which seem to be the norm on HS1 and French LGVs) and these 'arrow'-shaped ones?

The HS1 ones are TVM not ERTMS.

 

[hexagon789]

The HS1 ones are TVM not ERTMS.

Thanks, makes a lot of sense!