What is Greengo
Greengo is a VTL project that aims to provide real-time, centrally optimized traffic lights at low-cost for the general public.
In short, the system will leverage on phones to send real-time vehicle localization information to a centralized cloud backend and produce optimized traffic lights based on those information. The system can work even with partial penetration (i.e. even if not all drivers are running the Greengo app) by making physical traffic lights display the traffic light values computed by Greengo.
Have a look at the official website.