This captioned movie shows a shape-shifting wheel created by DARPA and Carnegie Mellon University's National Robotics Engineering Centre.
The Reconfigurable Wheel-Track mechanism can transition from a round wheel to a triangular track in two seconds. This allows vehicles to have enhanced mobility and manoeuvrability, and faster travel on a range of terrains.
When in its round form the wheel allows vehicles to travel quickly on hard terrain, while the tracks perform better on soft surfaces, by lowering the vehicle's ground pressure.
Launched as part of the US government's Ground X-Vehicle Technologies programme run by the Defense Advanced Research Projects Agency (DARPA), the Reconfigurable Wheel-Track system was designed to improve the mobility and effectiveness of combat vehicles.