My airline is removing the exit path lighting from our fleet, as it is prone to damage and can delay flights while it is fixed, and repairs can be complex when dealing with wiring under the cabin floor.
The exit path lighting is being replaced with photoluminescent strips on the floor of the aircraft along the aisle. Any gap in the strip down the aisle indicates an exit at that point - the system is that simple. The initial investment is high, the photoluminescent strips cost approx £300 per metre, but they are totally self contained, require no power source and very little maintenace, and most importantly are totally reliable!
Hopefully, over the lifetime of the aircraft the investment will be more than repaid in reduced maintenance costs, and improved reliability.
The photo below shows a Finnair 757 with the same photoluminescent strips - you'll have to look at the large version to really see them.
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Photo © Pekka Lehtinen
Not the best photo, but the only one I could find in the database. While still quite rare, I think this type of exit path marking will become very common over the next couple of years as airlines get over the initial costs and realise the long term cost and reliability benefits...