This article is about a new report from Arthur D. Little that predicts that interleaving autonomous vehicles with human-piloted ones on UK roads will actually increase traffic. The real-world simulation analysis demonstrated that purely autonomous vehicles would reduce urban congestion, but that a mix of robot and human drivers would increase traffic jams by over 16%. The micro-simulation focused on a major intersection in Frankfurt am Main, Germany, notorious for its evening traffic jams. The simulation measured the impact of three scenarios on traffic within the two central lanes: 100% human drivers, a 50/50 split of human and robot drivers, and 100% autonomous vehicles with adapted traffic rules. The micro-simulation found that whilst fully autonomous vehicles would solve this problem, the initial scenario we are likely to see, with a mix of robot and human drivers, actually leads to greater traffic jams.