In British English, a running in board is a large sign showing the name of the railway station on which it is found. The signs are intended to inform passengers of their location when on a train entering the station, possibly while still moving at speed. Some signs display the names of the previous and following stations on the line.
In normal circumstances, a two-platform station has one running in board on each platform situated near that end of the platform to which trains serving the platform run in, hence "running in board".