I've noticed on SEHS that you'll have a whistle board for one direction of travel, but there is not one present ahead of the same spot in the opposite direction. In this arrangement, some of the rural crossings are protected by train horns in only one direction and not the other. Is this typical on UK railways? Are there other other considerations that allow a whistle board to be omitted? Visibility from on foot at the crossing perhaps. I notice this on the North Kent Line in the down direction before Hoo Junction. There's no whistle boards protecting the spots that are protected in the up direction. You can clearly make out the crossing infrastructure in the tracks. There's another spot further down on the Chatham Main after Newington but I don't recall the exact direction or location. Anyway, just curious. Thanks
