Prompt: Pick a piece of interactive technology in public, used by multiple people. Write down your assumptions as to how it's used, and describe the context in which it's being used. Watch people use it, preferably, without them knowing they're being observed. Take notes on how they use it, what they do differently, what appear to be the difficulties, what appear to be the easiest parts. Record what takes the longest, what takes the least amount of time, and how long the whole transaction takes. Consider how the readings from Norman and Crawford reflect on what you see.
According the Chris Crawford's definition on interactivity - the traffic light button may barely fly. But it is commonly used by the public to alter their situation, and I'd consider that completely interactive. The traffic light button allows pedestrians to let the traffic light operation know that they would like to cross. This then, in a varying amount of time, makes the car traffic cease to allow pedestrians to cross.
It's interesting to watch the way in which people use the traffic light. Some are patient, press it once, and wait for the light to change while remaining unbothered by the amount of time it may take. Other's are much less patient, and will press the button multiple times as if each time will emphasize their urgency to cross and make the light change faster.
The easiest part, for the user, is simply the operation method. All it is, is a push of a button. The difficult part is probably just waiting, and not knowing when the light will begin to change - not knowing if your pressing of the button has actually worked.
The whole transaction can vary in time as traffic light buttons control a varying range of traffic levels. In low traffic areas, the button can work almost immediately. In high traffic areas, the button can take up to a couple minutes.
In the words of Norman, "attractive things work better." The traffic button has a very simple design - with nothing exceptionally beautiful or ugly about it. But, Sandro Engel and Holger Michel developed a system that takes aesthetics with user experience and functionality, to a whole new level. In Germany, there is a traffic light that allows you to play ping pong with the person that is across the street from you. I've attached the video below. I found this to be an incredible use of public interaction and attractiveness.