The simple use of traffic lights, using red, orange (or yellow) and green, to indicate our current social state. This is used at different levels of scale, from the individual, to meetings, to collective projects. In a shared business space, it is often difficult to determine what state people are in, or the openness of a meeting, and the social traffic lights offer a way to avoid needless interruptions and establish a working environment that is receptive and friendly.
A general rule of thumb is to recognise the traffic lights are not to indicate the internal state of the organism, but an outward declaration to others of their social openness. That is, although implemented by the individual, it serves a social purpose, hence it is a social ligament. Red means closed, and it is not advised to engage for whatever reason. Green means open, and engagement is welcome. Orange means engage, but do not interfere or contribute unless asked.
People indicate the state they are in using coloured badges, the traffic lights. When people gather, and are forming some kind of decision space, their individual colours will determine the state of the collective. And the social traffic lights could indicate various projects are underway at different periods of completion. It is important to emphasise the colours do not indicate the health of the project, or how far along it is in its process, but simply how open it is to others to contribute.