These overhead lights in the Santa Monica Place (a shopping centre, you saw it in the Day After Tomorrow when the characters fall through a snow bank on the skylight) in California show the availability of parking spaces in the garage, so you don’t have to drive down an aisle looking in vain.
The lights align nicely so it is really easy to both drive the end aisle and scan the side aisles looking for a space. Ain’t technology wonderful?
I saw those in Turkey too. There would be a digital display at the entrance to each level showing the number of spots available on each floor.
These sorts of digital displays are not only prevalent at ParkHaus in Germany, but in many larger cities, as you enter the downtown core there are also large signs at major intersections which indicate how many places in aggregate are free on street and at multiple parking garages.
I saw this type of parking availability in Dublin in an u/g parking area for a large shopping centre. I found it very useful.