During my trip to Singapore, i noticed that in Singapore, you can see how many empty parking spaces in several famous places on the streets because they put the information on a digital panels. The information is updated everytime there's a new car entering or leaving the place, so it's a real time update.
The concept is simple, but the visitors who are planning to go there can take the benefit of this features and decide whether it's a good option to go there or not. Why waste your time and money if there aren't any empty space for you to park your car (unless if you want to use public transportation such as buses or trains).
Since cars are not that much in Singapore due to strict car life cycle regulation, the numbers displayed is always over 500 and sometimes it even reach 1000 for big places, such as Suntec.