Na Califórnia, um triciclo é uma 'bicicleta'. Para operações diurnas, o único requisito real é que uma roda possa patinar.
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.
Requisitos de equipamento
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
(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).
No estado de Nova York, você precisa ter um sino ou dispositivo semelhante em sua bicicleta.
Eu pensaria que a verdadeira pergunta a ser feita é "um policial acha que é legal?". Se eles acharem que seu triciclo não é seguro, eles o impedirão de ser legal ou não, como provavelmente deveriam.