At a local mall the city installed 3 chargers which rarely is enough. when i came there today, there were several EV parked and each of them had a sign on their charge port or window. One Volt had a a sign saying that a flashing green light means its full and OK to unplugged. One Leaf who couldn't charge when arrived had a note to 'please plug me in when you leave'. A third one had a note, "OK to unplug after 6 pm". It was awesome to see how people really try to make the best out of the limited number of chargers and actively help each other. ... yes I also have signs with me that I put in my window saying when it's OK to unplug me.