Traffic lights don't really do anything, says Saffer, "they’re only a mechanical prop, a signifier of a social contract we’ve agreed to (and have written into law). They are a means of behavior change, and we (mostly) obey."
Then there is the yellow light: "The yellow light is by far the most sophisticated and cognitively challenging part of any traffic light."
The internet of things, in this case the internet of traffic lights, is making the contract managed by traffic lights more complicated:
"Of course, once a majority of vehicles (including bicycles) are connected to the internet, they could signal their arrival time and route to nearby traffic signals, allowing them to adjust accordingly. Once the traffic grid understands where people are going, it could very well make getting to destinations much faster and more eco-friendly."
Along those lines, a U.S. Department of Transportation study suggests that "responsive traffic signals could save as much as 10 percent of all motor fuel consumed–17 billion gallons a year."
Then there is the question of whether we might someday move beyond the traffic light.