Self-driving cars can make traffic slower

"There is a lot of research showing that automated vehicles can improve safety. The researchers accounted for four types of vehicles: human-driven vehicles (HVs); connected vehicles (CVs) -- which are driven by humans, but share information with other connected vehicles and with the control system that manages traffic lights; automated vehicles (AVs); and connected automated vehicles (CAVs). The researchers ran 57 traffic simulations to assess the impact of a host of variables on travel time through an intersection. For example, the researchers looked at how traffic would be affected by various combinations of HVs, AVs, CVs and CAVs. "However, it's difficult and expensive to assemble a mixed fleet of HVs, AVs, CVs, and CAVs in a connected traffic-control system.