Design Concept: Visibility of System Status

Item that exemplifies design concept: the door mechanism shown below.

There are a lot of locked doors around Harvard’s campus (and really any institution that has restricted areas)—but sometimes it is hard to tell which doors are locked and which are not. We’ve all tried to open a door that we did not know was locked, and perhaps even after discovering that it is locked, we wonder if it should be locked. The black square to the left of the door in the above photo signals the status of the door: red light means locked and green light means unlocked. In this way it is clear not only whether the door is locked, but also clearly indicates that the door should be locked at some times, and not at others.

Item that does not exemplify design concept: the door mechanism shown below.

This is a door mechanism typical for a professor’s office at Harvard. As should be the case, the glass is clouded to allow privacy, the door is shut for quiet, and the rooms are reasonably soundproof. However, when these professors have office hours, sometimes it is hard for students to know whether the professor is in his/her office or not. A knock may not be heard if the professor is in conversation or listening to music, and obviously the student cannot see if the professor is present. Opening the door seems like a simple solution, but then during down time (between students) the professor must endure unnecessary noise. This can result in students waiting outside the door—uncertain whether to go in or not—or even in nervous students trying to open the door to make sure the professor is not waiting for them. Thus the visibility of the system status (whether the professor is “in”) is unclear.

Improvement on the problematic door mechanism:

A simple fix to this issue is to have a two light system: a red light indicates that the professor is busy, and a green light indicates that a student is welcome to enter. This gets rid of the confusion of the current setup: if the light indicates “Busy” it does not matter whether the professor is in the room or not—it is clear to the student that he/she should not expect a response to a knock and needs to wait. On the other hand if the light indicates “Enter”, it is clear that whether the door is closed or not, the student is free to enter. Moreover, the professor can get quiet time in between students at office hours by having his/her door shut. This design also includes redundant cues because even someone who is colorblind can interpret the status of the system by seeing which light is illuminated and then associating that light with its corresponding label. Final note: the sketch above shows both lights illuminated for demonstration purposes.