How does radar support adaptive traffic light control?

Traffic congestion tends to occur when the number of road users increases. To alleviate congestion in cities, traffic management centers need to make data-driven decisions. For this, they require the most accurate data available from a highly reliable source, such as radar sensors. 

Radar sensors detect the presence and movement of various road users, including large trucks, cars, cyclists, and pedestrians. They effectively monitor real-time traffic density and trigger traffic lights timing to adapt accordingly, leading to smoother traffic flow. Unlike competing methods, radar sensors also provide precise speed information and have a long range, which is essential for estimating arrival times and queue length. 
Moreover, radar sensors provide real-time per-object data for infrastructure–to-vehicle communication. When combined with data from the on-board sensors of the connected vehicles, this “collective perception” enables a range of additional safety solutions. For example, they can give cyclists a head start over other vehicles or alert drivers when they are about to run a red light.