The basic system works like this: Each parking space in a garage has a small monitor above it, which detects whether the space is occupied or not. The monitors feed this data into a central computer, which processes the information and transmits it to display boards located throughout the garage. Upon entering the garage, you drive past a board informing you that there are, say, 6 spaces available on Level 1, 15 spaces on Level 2 and so on. Each level has its own board telling you which rows have available spaces; each row has a board telling you exactly how many spaces are available within it. And atop each parking space — placed high enough that it can be seen all the way from the end of a row of spaces — is a light, which turns green if the space is free, red if it’s occupied. (This last touch helps alleviate one of the banes of a parker’s existence: spaces that look empty from a distance, but turn out to be occupied by subcompact cars.)
All of this costs money, of course — around $400 to $550 per parking space — but for garages in high-traffic locations, that expenditure might make sense.