upright, Resembling a two wheeler (diamond frame) but with two
wheels at the back and the rider straddling the frame. Steering is through a
handlebar directly connected to the front wheel like a bicycle;
delta, is similar to an upright, with two wheels at the back and one
at the front, but has a recumbent layout. One or both rear wheels can be
driven, while the front is used for steering (the usual layout). Steering is
either through a linkage, with the handlebars under the seat (USS) or
directly to the front wheel with a large handlebar (OSS); and
tadpole (or reverse trike), a recumbent design with two steered
wheels at the front and one driven wheel at the back. Rarely (because of the
problem of tipping over at speed), the front wheels can be driven while the
rear wheel steers. Steering is either through a linkage and a tie rod to the
plates of the spindle assemblies (USS) or with two handlebars, each
connected to a steerer tube (usually through a bicycle headset, with the
handlebars acting as stems) and a tie rod between the plates of the spindle
assemblies (OSS).