According to ORS 801.348, a motor-assisted scooter:
Is designed to be operated on the ground with not more than three wheels;
Has handlebars and a foot support or seat;
Can be propelled by human or motor;
Has a motor capable of propelling it no faster than 24 miles per hour on a level road; and
Has a motor no bigger than 35 cubic centimeters or, if electric, has a power output of no more than 1,000 watts.
According to ORS 801.345, a moped:
Is designed to be operated on the ground upon wheels;
Has a seat or saddle for use of the rider;
Is designed to travel with not more than three wheels in contact with the ground;
Is equipped with an independent power source that is capable of propelling the vehicle, unassisted, at a speed of not more than 30 miles per hour on a level road surface; and if the power source is a combustion engine, has a piston or rotor displacement of 35.01 to 50 cubic centimeters regardless of the number of chambers in the power source; and
Is equipped with a power drive system that functions directly or automatically only and does not require clutching or shifting by the operator after the system is engaged.
A bicycle equipped with a power source may be classed as a moped if it meets all the moped requirements and also does not meet either the definition of an electric assisted bicycle as defined in ORS 801.258, or a motor assisted scooter as defined in ORS 801.348.