I thought it was going to be something that used vision to monitor the roadways and dynamically make decisions about the lights, which would be a very different way of controlling traffic. It's a predictive model of traffic that they used to adjust light timings, which is the same way that traffic has always been controlled, informed by a model. It's nice that it helps, but they probably had no shortage of decent ways to model traffic that would have led to this result. My guess is no one looked into it and Google found an easy place to showcase an AI model.