Photograph by DCTWINKIE5500on Flickr.
Trailer bike (also known as a trailer cycle or a third wheel, The rider of a BogotÃ¡s Bike Paths Network trailer bike usually has a saddle, handlebars, and pedals. They seldom have brakes. A trailer bike is attached to a bicycle at either the seatpost or on a special rear rack by a linkage that allows for pivoting.
Some fold for more compact storage. The trailer bike was patented by Canadian entrepreneur, Delbert Adams.