All of my significant accidents while commuting have been solo and due to more-or-less unforeseeable loss of traction. Using hindsight, I now am alert to the particular circumstances that caused the loss of traction; but I'm far from having a universal formula for avoiding all possible causes of losing traction. The biggest unknown is the surface itself. Until you've lost traction on a particular patch, you don't know what its limiting traction is, and you tend to assume it is same as the apparently same type of surface anywhere else, which is not always a good assumption, I've found.