On topic:
Some/several escape routes do have artificial lighting off at normal times, with fire escape light switches at each level to turn on normal lights and non maintained escape lighting units for power failure.
Even new or refurbished premises sometimes keep this practice, but replacing the reliance on light switches with PIR activation.
This is because, especially in larger buildings, it is prohibitively expensive to keep stairs mainly or solely used for emergency purposes lit 24/7 or even just occupied hours year round and RP's will not do it.
Plus just the photoluminescent signs alone are not sufficient for escape & despite extolling the benefits of a full way guidance system most RP's won't go for it - I've only ever got one true system in for a specific risk area of a building.
Off topic:
I didn't mean you were plugging it per se, but Jalite has entered the dictionary as a common term for photoluminescent material just as Hoover is commonly used as a term for vacuum cleaners.
This is of course due to their high market share resulting from high standard of their product, continuous development & very good technical support and guidance documents - their illustrated guide to fire signage is a great tool to give end users as is easier to understand and cheaper than copies of BS 5499-4.
But to paraphrase the BBC ads "other manufacturers are available". Most don't achieve the performance of Jalite AAA, but everlux/masterlux by Sinalux in Portugal has a very good range with good performance. Not known to end users, but being used by a number of companies in the fire trade