I’m constantly encountering sensors on my day-to-day moveabouts. Whether I notice them or not, sensors facilitate how I move throughout my neighborhood and the city at large. Some are more hidden than others, like the sensors that control the traffic lights. I don’t notice these sensors/cameras unless I’m really looking for them. Others are more blatant: crosswalk buttons, OMNY tap surfaces at the various subway stations, and my own mobile device.

When it comes to sensors that are less noticeable, they don’t make themselves known until I want to do something like walk across the street, pedal faster on the Citi bike or see how much time/distance I have remaining to get to my final destination. At that point, I seek them out in order to do something or change states, and that’s how I know when a sensor has sensed something: once I notice a change in states. I know a sensor has done its job once I am directed to cross the street safely, when an automatic door has opened for me, or when the security gates in the lobby recognize my ID card and grants me access.

Depending on the sensor itself, there may be more than one stage of interaction while others that are more simple require only one. An example of a sensor (or group of sensors) that has more than one stage of interaction is the Citi bike. I use a camera sensor to scan/unlock the bike, the sensors in my phone talk to the sensors in the bike to denote where I am location-wise, and the bike racks themselves have sensors to detect when I’ve returned the bike/ended my trip. An example of a single-interaction sensor would be an automatic door sensor.