… Surtrac (Scalable Urban Traffic Control), which uses a hybrid stoplight bundled with video cameras and a Surtrac processor.

Here’s how it works: When the video cameras see approaching traffic, the Surtrac processor computes a plan for how all of the vehicles are going to move through, Smith says. The stoplight then follows Surtrac’s plan, streamlining traffic flow, and Surtrac shares the data with other stoplights to minimize cumulative delay for a larger area.

In results announced last September, the pilot reduced travel time by 25% and cut vehicle emissions by 21%. …

Carnegie Mellon Today, Vol.10, No. 2: Green Light