London Underground “Way out” & connecting line wall signs, 1998
These yellow and black “Way out” signs, plus directions to connecting lines, are liberally placed along the platforms. They’re conveniently placed directly across and a bit above eye level as you’re exiting a train. One trick when you’re on a train entering a station where you’re going to exit or switch lines is to look out the windows of the train at these signs as the train is slowing and coming to a stop. This lets you know as soon as you step out onto the platform whether to turn left or right to get to the exit or a connecting line.
I’m pretty sure this was on the Picadilly line, at Holborn station.