Soft surfaces are better for a track. Hard surfaces are best for wheels. DARPA's Reconfigurable Wheel-Track delivers both in a single package. Developed by a team from Carnegie Mellon's National Robotics Engineering Center, it's able to switch from a triangular, tank-like track to a round wheel or back again in as little as two seconds, letting soldiers adjust as needed and on-the-fly to changing terrain. It's part of the Ground X-Vehicle Technologies (GXV-T) program, joining tech like crew augmentation systems, in-hub motors, and an extreme suspension.