Uber Black is the service in which ride requests are answered by drivers of "black cars" similar to the Lincoln Town Cars used by NYC car services (sometimes even limos). The drivers are experienced and drive as their primary job, rather than being, like Uber X, moonlighting amateurs using their private cars.

These full-time drivers are much more likely to know the nuances of traffic patterns and to know of alternative routings. All this at a substantial price differentiation front Uber X, but essentially, you get what you pay for.