How well does the Tesla Model Y's well-known Full Self-Driving system work? After spending several days letting it do its thing on the roads and highways surrounding Car and Driver's Ann Arbor, Michigan, offices, as well as in San Francisco, we can report that it works impressively well. Most of the time. In most driving situations. Usually. With an asterisk. That asterisk comes courtesy of Tesla. The correct name for the feature is "Full Self-Driving (Supervised)." The word in parentheses says it all.