This is not true. Automotive radar are in the ~80ghz range, giving it a wavelength on the order of about 4mm. Car radar can definitely see through rain and sno

This is not true. Automotive radar are in the ~80ghz range, giving it a wavelength on the order of about 4mm. Car radar can definitely see through rain and snow. All radars receive a range of reflections from many objects, rain included, but the return off of rain is nothing compared to the return off of a solid object. The filtering then becomes choosing the peak amplitudes of the radar return signal. Rain will manifest itself as a smearing of the signal and lowering the peak a little bit, but usually much less than a solid object. Optical and lidar work miserably through rain/fog, with wavelengths in the ~1000nm range, but have much higher resolution. Any real self-driving solution in the near to medium future is going to involve sensor fusion of as many sensors the car manufacturers can afford and cram in. This means cameras, ultrasound, lidar, radar, etc. Anybody telling you that there is only one true sensor to rule them all is either selling you something or ignorant of the state of the industry