Speed Board In Tunnels

There is also light box type I don't have a picture of one though

Like this one?



Good point. This was on the Northern line West End branch, just outside Mornington Crescent as we approach the junctions at Camden Town. Once again borrowed from a Video125 Driver's Eye View video.

Yes indeed

I suspect when the specific sign was installed would likely play a part.

For example, externally illuminated signs went out of fashion some time ago, nowadays standard practice is reflective signs. However things don't tend to be changed retrospectively unless something else is occurring in the area. Same with T boards - current policy is to indicate the actual permitted speed, but there are still plenty of T boards to be found. In summary, things are rather inconsistent from place to place let alone line to line. Drivers line and route knowledge comes into play accordingly.