You can't always decide when you have to drive. If you're on the road and conditions worsen then it may be safer to drive until you can get off the road safely. I've been in rain squalls so heavy that you couldn't see anymore and that is when it gets tricky: you know you should stop driving but that risks being rear-ended by someone who disagrees with you. A self driving car would end up being rear ended just the same.

Stopping traffic only works if everybody starts out with the same playbook in mind.

But to start driving in those conditions (or even if those conditions are likely to occur) that's madness, unless you are a first responder.