I don't think any of those examples are edge cases. The first set are normal traffic conditions that in the context of self-driving cars are easy to solve, especially in narrowed conditions such as on a highway. Moreover, mid-range cars already have collision warning and automatic braking systems. As to your example of traction issues, pretty much every modern car that I'm aware of has had computer assisted traction control systems for a while now.

The edge cases that are difficult essentially boil down to entity recognition; unexpected and moving obstacles, road sign changes, traffic light outages or alternate signal pathways and the like. Some of those definitely would require government level coordination which is about a lot more than technology.