Even in broad day light and hith High Res videos and with ML algos, we cannot extract all information accurately that are needed. For example, at what velocity the other vehicle is moving and also at what distance we have an obstacle etc. is very difficult to extract from camera alone and impossible when it is night or extreme weather conditions. Hence we need Radar & Lidars also for ADAS & Self driving applications.

Radar: It can accurately measure Distance and Velocity information of objects around ego vehicle and also can track objects. It works well in all weather conditions (Day/night/rain/fog etc). Lidar: Good distance measurement, Rich in data (3D Point cloud) for ML, OK in doing classification (pedestrain, bicyclist etc) even in nights. But expensive sensor.