An autonomous vehicle including a body defining a door opening for a front door and a rear door. The doors are attached to the body a track that guides the doors between an open position and a closed position. A rocker assembly includes an outer rocker panel defining a slot, an inner rocker panel attached to the outer rocker panel, and an insert including an upper tube and a lower tube disposed between the outer rocker panel and the inner rocker panel. The tubes extend between a front end and a rear end of the rocker assembly, a track is assembled between the upper and lower tubes, and the slot in the outer rocker panel provides access to the track for brackets that have rollers that engage the track. The brackets are attached to the doors.