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Surtrac: Pittsburgh’s Problem-Solving, Artificial-Intelligence-Enabled Traffic Lights

As we saw in 2001: A Space Odyssey, you never want to create an AI named HAL 9000 and embody it in an illuminated red circle. But if you give it additional circles of yellow and green and name it Surtrac, it turns out it can be quite helpful.

Surtrac is the name of an artificial intelligence system developed by a company called Rapid Flow Technologies, and it lives inside of traffic lights. It’s been programmed to understand traffic theory, is connected to radar sensors and cameras, and can “talk” to other Surtrac lights.

What’s interesting about the Surtrac system is that it’s decentralized. Each Surtrac light makes its own decision whether to display red, yellow or green based on what it senses in its own intersection as well as after parsing data transmitted from nearby Surtrac lights. It then beams data it has generated back to the other lights, building a real-time knowledge base.

It sounds crazy, but it’s not a mere concept—it actually works. Pittsburgh has been trialing them since 2012, when RFT installed Surtrac lights at nine intersections in a particularly traffic-troubled neighborhood. “The crossing of three major roads (Penn Circle, Penn Avenue, and Highland Avenue) leads to changing traffic patterns throughout the day, making it difficult to manage congestion with conventional traffic signal control methods,” the company writes. “Surtrac reduced travel times more than 25% on average, and wait times were reduced an average of 40%.”

Those are encouraging figures. In addition to the time saved, emissions were reduced by 21%, and motorist stress was presumably reduced. All of those reasons have led Pittsburgh to green-light, if you’ll pardon the pun, more Surtrac lights; as of this year there are 50, and more will be added.

That’s the beauty of having a decentralized system—new lights can literally be added one by one, which is sure to be a boon to cities with budgetary constraints. RFT describes this feature as “Saving money with scalable deployments:”

Surtrac is a completely distributed system, designed to be robust to the uncertainties of traffic control. With no centralized computational bottlenecks, Surtrac deployments can easily grow incrementally to extremely large networks, and as new intersections are added, performance at existing Surtrac intersections will continue to improve.