The StreetFlyer vehicle, developed by Dr. Carsten Mehring, is supposed to represent a land version of hang gliding. The rider is suspended in a harness from the top. She steers with her hands and pedals the rear wheel. Mehring asserts that the StreetFlyer could serve physical rehabilitation purposes as it puts limited stress on the user's limbs.
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No helmet? Were collisions ever considered?
Lock the front wheels on a hill and the only thing saving you from smashing your face is a design which will flip over forward and body slam you onto what appears to be 2" steel tubing. I will bet this thing could not even handle tagging a curb as the friction would pull the erring front wheel into the curb further while lifting that corner of the elongated triangle. Doooom.
Flaw: nobody hang glides in the city. It's too impractical. It would be worse trying to do it from the ground.