Comment by BugsJustFindMe

I said favorable circumstance, not favorable conditions. I mean the person in front of you doesn't stop quickly or veer into your lane very often regardless of whether there is e.g. fog or some confusing signage. Knowing what to do in a confusing situation is a hard problem, but avoiding a crash when someone stops abruptly with full visibility requires mostly safe management of speed, distance, and lane exit options, which people are terrible at.