It uses a fixed-gear bike not out of trendiness but for a more simple reason: the robot would have a tough time managing a freewheel, which allows the back wheel to spin even if the robot stops pedaling. Also, a fixed-gear allows the robot to brake simply by slowing or applying reverse pressure to the pedals. He stops the same way you and I do: by taking his feet off the pedals and balancing on his toes. Perhaps the world's most failsafe electric brakes are a bit too complex for this minimalist robot cyclist.