Spoiler:
The signs only show general direction.
Hospitals and other large buildings sometimes use lines on the floor or walls to help people find their way around. Valve used them in Half-Life, and they seemed like a natural part of the environment. The gameplay function was invisible.
We already have floor decals to use for this. The only problem is they're a pain to map, like old cables. It'd be better if they worked like smart cables. Smart cables don't need a direction set and connect to adjacent cables by themselves. You'd only need to specify a pixel offset so more than one line could go on the same tile without overlapping.