A velomobile or bicycle car is a human-powered vehicle, enclosed for aerodynamic advantage and protection from weather and collisions.^[1] They are virtually always single-passenger vehicles. They are derived from recumbent bicycles and tricycles, with the addition of a full fairing (aerodynamic shell). There are few manufacturers of velomobiles; some are homebuilt. Some models have the operator's head exposed; this has the advantage of giving the operator unobstructed vision, hearing, and some cooling, with the disadvantage of being more exposed to weather and less aerodynamic. Similar vehicles that are not human-powered are instead called microcars.