Vehicle with foldable double-wheel assembly

1. A vehicle with foldable double-wheel assembly having two states, a first state as a pedaled tricycle and a second state as a running bike, comprising:

a frame;

a single-wheel assembly;

two pedals for driving the steering wheel to roll, in said first state;

a handlebar assembly matching with said single-wheel assembly for control steering;

a double-wheel assembly, where said double-wheel assembly comprises a supporting beam and two wheels disposed on said supporting beam, wherein said supporting beam comprises two branches of same structures, said two wheels being respectively disposed on said two branches, said supporting beam having a first state, as a pedaled tricycle, where said two branches are open, and a second stable state, as a running bike, where said two branches are put together side by side and wherein said supporting beam further comprises a coupling assembly for rotatably coupling the two branches to said frame and a pivot for rotatably coupling said two branches to said coupling assembly, wherein each said branch further comprises an extension arm, extending from said coupling assembly, wherein said extension arm comprises an outer tube extending from a side of said coupling assembly; and

wherein the extension arm further comprises an inner tube connected to said outer tube, an end of said inner tube being extended into said outer tube while two mounting arms being disposed at the other end of said inner tube.

2. The vehicle of claim 1 , wherein the tricycle comprises a footrest.

3. The vehicle of claim 2 , wherein the footrest is a foldable footrest.

4. The vehicle of claim 1 , wherein the pedals are foldable pedals.

5. The vehicle of claim 1 , wherein the pedals are attachable-detachable pedals.

6. The vehicle of claim 1 , wherein the two wheels in said double-wheel assembly are aligned in parallel with each other when said supporting beam is in the second stable state.