The only time I ever get in a cab is when it is pouring rain, so this does not make a lot of sense to me, but it may be "a more sustainable alternative for a fast and flexible travel" from designer Gert-Jan van Breugel.
"The City Swing is a hybrid motorbike cab with seats for three people. Driven by bio-fuel or electricity, and by making use of bus-only lanes, the motorbike cab is faster, more economical and less polluting than present-day cabs."
City Swing's on Broadway means no air pollution and no engine noise. ::Gert-Jan van Breugel via ::Core77