This handoff is something human-machine interaction designers have spent a lot of time puzzling over. Today, research published in the inaugural issue of the journal Science Robotics highlights a new bump in the road: Human drivers may not be capable of smoothly taking control of their self-driving vehicles. The research, co-authored by a multidisciplinary group at Stanford University, studied 22 drivers on a 15-second course containing a straightaway and a lane change. The car navigated itself to the start of the course, then handed control over to the driver, who negotiated the straightaway before being cued to make the lane change.