I am a freshman in high school who is planning to build his own recumbent tricycle. However, I would be very disappointed if my creation was illegal to ride on bike paths and sidewalks. I have already perused the Wisconsin State Statutes, and there is nothing that would apply to even a store-bought tricycle. Is anybody aware of laws from other states covering tricycles, so that I may be aware of them before I start building?
These are the Wisconsin State Bicycling Laws:
340.01(5) defines a bicycle thusly: "Bicycle" means every vehicle propelled by the feet acting upon pedals and having wheels any 2 of which are not less than 14 inches in diameter.
As it makes no mention of where or how the machine was manufactured, it sounds like your tricycle (and its rider) will be held to the same legal standard as any other bicycle. The wheel size requirement means that if two wheels are larger than 14 inches, it's a bicycle. My guess is that this is intended to rule out kids' "Big Wheels" and the types of tricycles that a 5 year old might ride.
That said, it's worth reading the entire document. I didn't bother because I don't live in Wisconsin.
It's also worth noting that local municipalities can pass further laws defining or restricting bicycles as long as they don't conflict with the state laws. So you'll want to check those as well. Those are sometimes hard to locate on the internet. If you have can't find them online, check out your public library. They usually try to archive local information like that.
Finally, as others have mentioned, the sidewalks are often illegal and even more often dangerous places to ride. If you do so, do so with great caution.
In California a tricycle is a 'bicycle'. For day time operations the only real requirement is that one wheel can skid.
39000. "Bicycle," for the purposes of this division, means any device upon which a person may ride, which is propelled by human power through a system of belts, chains, or gears having either two or three wheels (one of which is at least 20 inches in diameter) or having a frame size of at least 14 inches, or having four or more wheels.
21201. (a) No person shall operate a bicycle on a roadway unless it is equipped with a brake which will enable the operator to make one braked wheel skid on dry, level, clean pavement. (b) No person shall operate on the highway a bicycle equipped with handlebars so raised that the operator must elevate his hands above the level of his shoulders in order to grasp the normal steering grip area. (c) No person shall operate upon a highway a bicycle that is of a size that prevents the operator from safely stopping the bicycle, supporting it in an upright position with at least one foot on the ground, and restarting it in a safe manner. (d) A bicycle operated during darkness upon a highway, a sidewalk where bicycle operation is not prohibited by the local jurisdiction, or a bikeway, as defined in Section 890.4 of the Streets and Highways Code, shall be equipped with all of the following: (1) A lamp emitting a white light that, while the bicycle is in motion, illuminates the highway, sidewalk, or bikeway in front of the bicyclist and is visible from a distance of 300 feet in front and from the sides of the bicycle. (2) A red reflector on the rear that shall be visible from a distance of 500 feet to the rear when directly in front of lawful upper beams of headlamps on a motor vehicle. (3) A white or yellow reflector on each pedal, shoe, or ankle visible from the front and rear of the bicycle from a distance of 200 feet. (4) A white or yellow reflector on each side forward of the center of the bicycle, and a white or red reflector on each side to the rear of the center of the bicycle, except that bicycles that are equipped with reflectorized tires on the front and the rear need not be equipped with these side reflectors. (e) A lamp or lamp combination, emitting a white light, attached to the operator and visible from a distance of 300 feet in front and from the sides of the bicycle, may be used in lieu of the lamp required by paragraph (1) of subdivision (d).
In New York State you have to have a bell or similar device on your bike.
I would think the real question to ask yourself is "will a Police Officer think it is legal?". If they think your tricycle is unsafe they will stop you whether it is legal or not, as they, most likely, should.