On the contrary, I would think if eventually all vehicles become autonomous and coordinated via a centralised network, traffic would flow much more smoother. If there are hazards or obstructions on the road, this information would be relayed to the central controller and all vehicles would be re-routed to minimise impact to traffic flow. With such a system, the flow direction of a lane cold even be changed at short notice as required, greatly optimising the usage of roads leading to improved traffic flow. Also, since computers have much faster response time compared to humans, and because there're no idiots at the wheel, the speed limit could also be increased significantly.