There you are, standing on a street corner surrounded by a mob of people waiting for the walk signal. In front of you, a single car gets the green light. Again. For all the talk of smart cities, they can be infuriatingly dumb at times. But imagine if your city could monitor the flow of pedestrians and optimize its traffic signals for walkers, not drivers? That’s exactly what Chicago is looking to do.

Later this fall, the Windy City will install a network of 40 sensor nodes on light poles at the University of Chicago, School of the Art Institute of Chicago and Argonne National Laboratory. The goal is to eventually expand the system to 1,000 sensors (enough to cover the Chicago Loop) over the next few years. Spearheaded by the University of Chicago’s Urban Center for Computational Data, it’s called the Array of Things initiative, and the goal is to gather an unprecedented set of ambient data to help government officials and residents understand how their city ticks so they can make it a happier, healthier, and smarter place to live.

Every 15 seconds these sensors will gather information like temperature, humidity, carbon monoxide, vibrations, light, and sound—pretty standard stuff. But Charlie Catlett, director of the Urban CCD, says gathering even basic data can help us to evaluate some of our cities' most unquantifiable features like hyper-local air quality, pedestrian traffic, emergency route efficiency, and resource allocation like salt for icy roads. “Right now, we don’t have any scientific data that proves if you do X, Y, or Z, it will improve walkability,” he says. “I’m interested in collaborating with architects and designers to see if we can put some data behind the rules of thumb in urban design.”

Catlett imagines that some day people will be walking down the street and their phones will automatically pull in the data that the sensors have gathered over bluetooth. This could be used to alert you to the most well-lit path during a late-night walk home. Or it could eventually be used to track air particulate, which could shed light onto why allergies or asthma is more common in certain areas of the city and help inform health policy. Another useful application is adding context to the data your fitness applications gather. “Now at the end of the week you can look at the number of steps you took but you can also look at: What was my exposure through the week to carbon monoxide or excessive noise?” says Catlett.

A City That Knows Its Own Heartbeat

More audacious yet is the plan’s goal to track the foot traffic throughout the city. Catlett says the team has been discussing ways to do so in a privacy-first way, and so far they’ve landed on embedding a Bluetooth modem in the sensor. The idea is that the as people walk by the Bluetooth modem would ping their phones and return clean data back to the modem, counting each device as a person. This could help shift traffic priorities to pedestrians and avoid the scenario we wrote about at the beginning of the story. “You have this situation where you might have 150 people on the street corner waiting for a walk light and there’s only one car that needs the green light,” says Catlett. “The city is set up to bias its operations toward vehicles.”

The plan has come under scrutiny by some pro-privacy groups who worry it enters into Big Brother territory, but Catlett says the data they’d get from the phones wouldn’t even register the device’s IP address. John Tolva, Chicago’s former Chief Technology Officer says there’s an important distinction to be made between observation and surveillance. “It’s important to remind people that being closely observant of the urban fabric is what makes cities better,” he says. There are shortcomings to using Bluetooth as an indicator of population. Not everyone has a bluetooth-enabled device, and those that do don’t necessarily activate it on a daily basis. Still, it’s an upgrade to an otherwise archaic system. “In 2014, state of the art is sitting at an intersections with a clipboard," says Tolva. "It seems like we can do better than that."

Making Hidden Data Useful With Open Source

To be fair, cities are already gathering plenty of environmental data, just not at this resolution. Bridges sensors can alert us to icy conditions, street lights track vehicle motion and issue us tickets when we run red lights. Problem is, much of this data is locked away, for no one to make use of. Open source data gathering has just begun. Cities like Amsterdam and Barcelona are using the Smart Citizen Kit to monitor things like noise, air pollution and traffic.

The difference here is all of the data will be fed into an online, open-source portal that anyone can access. The hope is that citizens will tap into it and create applications that go beyond typical civic worries like icy roads. It’s an ambitious project, but right on trend with the growing quantified-self movement. “We think of this project as an extension of that,” Catlett says. “It’s like OK great, you have a Fitbit—now the city has a Fitbit.”