Detection of abnormal conditions might be tractable (though I wouldn't call online vision or recognition trivial problems). But taking action is harder. A piece

Detection of abnormal conditions might be tractable (though I wouldn't call online vision or recognition trivial problems). But taking action is harder. A piece of debris might manifest in a way that causes a self-driving car to skid to a halt or swerve - dealing with abnormal conditions in real time on crowded roads is certainly not a trivial problem, especially given the stakes.