So, the intelligence of a mouse, crow, parrot, dog, cat, monkey, elephant, dolphin, orca, etc. just is not enough.
So, self driving cars requires essentially full AI for driving and nearly everything else in life. So, the self driving car problem is no easier than the full AI problem.
Sure, there can be some special cases that are easier -- trucks in a huge, open pit copper mine, a tractor on a huge, flat farm in Missouri, some military battlefield situations, and the public roads if heavily reengineer them with lots of essentially electronic tracks, etc., uh, right, on roads in perfect condition, no big objects falling off trucks, no drunks, no tire blowouts, dry weather, daylight, perfect visibility, no alarms from an extensive monitoring system, and no rain, sleet, or snow. Then, sure, a "self-driving car"!!!!