DARPA researchers have created a reconfigurable wheel-track technology that’s capable of altering a wheel’s shape and function whilst the vehicle is in motion. the RWT allows vehicles to tackle various environments, transforming the wheel in approximately two seconds.


video by DARPAtv

changing from a round wheel to a triangular track and back, the wheels permit fast travel on hard surfaces while tracks perform better on soft surfaces. their practical use includes military uses including search and rescue, or perhaps in construction. 
DARPA wheels switch from tires to tracks while vehicle is in motion
the wheels are far off being realised on production vehicles however. DARPA is in phase two of a broader ground X-vehicle technologies program which includes developing the shape-shifting wheels as well as other technologies. these include an in-hub electric motor (aiding speed and manoeuvrability), multi-mode extreme travel suspension (enabling stabilised high-speed travel over rough terrain), virtual windows (enabled with 3D goggles), and sensor-enhanced virtual perspectives and visual overlays that aid in safe off-road navigation.