Interesting implementation of the 2 wheel non-tandem concept.
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http://www.peugeot-concours-design.com/en/01_vainqueur/
http://digitalcamera.101reviews.com/...s-into-reality
Doesn't seem to be self-balancing and, from the description, there is a "caster" up front, so technically it's a tricycle. But it does use the two large wheels for differential steering.