Exit signs are a common sight in most buildings. Typically, these are somewhat unobtrusive signs, located quite near to the doors. Many have been designed to be illuminated in the event of a power failure.
I say that these exit signs are unobtrusive for two reasons. For one reason, they are a little
bit small for today's typically somewhat myopic office worker. For another reason, they are always visible.
Fluorescent lights are a common sight in most buildings as well. In the event of a power failure, the most obvious difference will be that those lights are no longer working.
Therefore, I suggest that in the event of an emergency, the most obvious place for an exit sign would be incorporated into the fluorescent light fixtures themselves.
Many of these fluorescent light fixtures are already rectangular, and quite large. Often they have a cover, with an opaque film on it.
Photoluminescent material can be made into an opaque powder, and incorporated into paints. This can then be painted onto the cover of the fluorescent fixture in the form of an exit sign. The photoluminescent material would then be a few inches from the lights, and would be charged all day, for slow release when the lights go off. Even 30 seconds of charging from a source so close would suffice to keep the material glowing for a few hours. That ought to be enough for most any exit plan.
The result would be large exit signs, located at the precise place people would look in the event of a power failure, and already charged to be bright long enough for most reasonable exit plans.
Due to the fact that fluorescent light fixtures are not always placed right in front of doors, additional exit signs might still be necessary, but an exit sign on every fluorescent light would (in buildings equipped with fluorescent lights) certainly provide better direction than the current setup.