The networked sensors and signals in Ann Arbor give the city a coordinated way to respond to traffic.

We've all thought, "Why is there a light here?" when stuck waiting for a signal to change on an empty street. In Ann Arbor that frustration may be going away. "To combat congestion, each hopped-up signal uses pavement-embedded sensors or cameras to spot cars waiting at red lights. The signals send that information via fiber network to the Big Computer back at traffic management base, which compiles the data," Aarian Marshall reports for Wired. This technology has already been implemented in cities big and small around the world, but the Ann Arbor system takes the application further. "If there are four cars lined up to go one way through an intersection, and zero cars lined up to move perpendicular to them, the light might turn green for the four. But a network of connected lights—like in Ann Arbor—will analyze the entire grid, and figure out who to prioritize to get the most people to their destinations the fastest," Marshall writes.
While this technology can alleviate some inefficiencies in commuting, it can only go so far in speeding up automotive transit times. "Geometry says there are only so many ways to fit a bunch of vehicles on to streets," Marshall writes. Further, the phenomenon of induced demand will likely cause new drivers to take up the slack the system creates.
FULL STORY: Ann Arbor Is Fighting Traffic With Software—and Winning

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