This sign was curiously different, rather than "We have 786 spaces where you aren't", it looked like the information might change.
One of my daughters asked "What are those lights for?" and before you could see "geek car park love in" all was revealed.
It's a wonderful arrangement, when the space is empty the light is green (see above). When the space is occupied (by a car or silly people), the light is red (below). So when I drive around the level I can see where to aim my car without the hassle of driving up and down trying my luck.
If you deserve a special space, you get a blue light (no disco, sorry).
What struck me was that someone thought about what you want from using a car park - a space as fast as possible and or as convenient as possible - and came up with a nice way to help the driver achieve that goal. Having been back on a wet day with the car park near full, it was fantastic, child yells out "there's a green light" and off we go to the empty space. There was only a short drag race with another car heading for the spot, but my van had the momentum, they backed off and we won, woohoo.