This contraption, the bricycle, is in vital ways intermediate between being a bicycle and being a tricycle, it is adjustable to act as the one, or the other, or something inbetween (a better name for it might have been biandortricycle). The bricycle is said (and demonstrated here) to be almost unridable. Its the work of Owen Dong, Christopher Graham, Anoop Grewal, Caitlin Parrucci and Andy Ruina at Cornell. They have done a fair amount of research on what makes bicycles work and not work.
Kim Krieger, writing in Science Now, essays a look at the world of the bricycle.
(Thanks to investigator Steven Strogatz for bringing this to our attention.)