That small white box mounted near some traffic lights is often a LiDAR traffic sensor, designed to monitor activity around an intersection.
Instead of taking traditional camera images, LiDAR sends out laser pulses to map and track vehicles, pedestrians, bicycles, and other road users.
Sensors may be positioned on different sides of an intersection to provide broader coverage and help with traffic counts and signal management.
They’re increasingly being used as traffic technology advances, although the exact purpose and capabilities can vary depending on the device and installation..See below