State-of-the art 79 GHz automotive radar: 0.2 m range uncertainty, 5 degree azimuth angular uncertainty, dozens of points per second.
Spinning lidar: <0.05 m range uncertainty, <0.1 degree azimuth angular uncertainty, a million points per second.
Radar definitely has its uses as it can see through weather conditions and tell velocity, but lidar is the vastly superior sensor otherwise.
That is far from what is currently considered advanced for mm-wave radar in 93-95ghz range - 0.5 degrees
Google "GPU Acceleration of SAR/ISAR Imaging Algorithms" and see how much you can get with with regular high bandwidth 10ghz radar and computing power in tenths of gigaflops.
I worry that these modern cars will be basically requiring fighter jet storage in order to work. I need something that works in a snowstorm when the car is covered in ice.
My "parking sensors" (the cheap little distance sensing thingys mounted around most new cars) are screaming every time there is a little surface ice over them. I work around this by simply ignoring it. But if a car would require these sensors to function, which would be the case if it was autonomous, I'd be starting my morning drive by somehow getting the ice off them.
Generally, to increase resolution you can do following - increase antenna size, increase number of antennas, increase amount of processing power thrown on it.
Right now, existing offerings can be improved in all 3 ways with ease.
Commies had them in such abundance that they put millimetre wave imagers (and that was in seventies) on thing as cheap as vision aids for tank drivers, field guns, single shot atgms, and even small arms.