From USC 49 Section 32101
USC 49 Section 32101
(7) ''motor vehicle'' means a vehicle driven or drawn by
mechanical power and manufactured primarily for use on public
streets, roads, and highways, but does not include a vehicle
operated only on a rail line.
(8) ''motor vehicle accident'' means an accident resulting from
the maintenance or operation of a passenger motor vehicle or
passenger motor vehicle equipment.
(9) ''multipurpose passenger vehicle'' means a passenger motor
vehicle constructed on a truck chassis or with special features
for occasional off-road operation.
(10) ''passenger motor vehicle'' means a motor vehicle with
motive power designed to carry not more than 12 individuals, but
does not include -
(A) a motorcycle; or
(B) a truck not designed primarily to carry its operator or
passengers.
(11) ''passenger motor vehicle equipment'' means -
(A) a system, part, or component of a passenger motor vehicle
as originally made;
(B) a similar part or component made or sold for replacement
or improvement of a system, part, or component, or as an
accessory or addition to a passenger motor vehicle; or
(C) a device made or sold for use in towing a passenger motor
vehicle.
This tub does not meet the definition of motor vehicle, since it can not by itself be driven or drawn by mechanical power on public roads, streets or highways. It does however meet the definition of "passenger motor vehicle equipment"