This is usually called adaptive traffic control, and has been implemented (minus machine learning, I'm guessing) in a bunch of places, including a part of New York City [1] and, more famously, Australia [2]. The latter system, pioneered by the city of Sydney, has been sold to other countries such as Singapore. Not sure how technologically interesting these systems are. The Sydney system was developed in the 1970s, but has been improved with more modern tech (such as cellular networking) since then.

[1] http://www.nyc.gov/html/dot/html/pr2012/pr12_25.shtml

[2] https://en.wikipedia.org/wiki/Sydney_Coordinated_Adaptive_Tr...