The moped definition, precisely
RCW 46.04.304 defines a moped as a motorized device travelling on not more than three wheels in contact with the ground, with a motor that:
- does not exceed fifty cubic centimeters of displacement,
- produces no more than two gross brake horsepower, and
- is capable of propelling the device at no more than thirty miles per hour on level ground.
All three, not any one. This is why a 49cc scooter that has been derestricted to do 40 mph is no longer a moped in the eyes of the law.
What a moped gets you
RCW 46.20.500 exempts mopeds from the endorsement requirement: a person 16 or older holding a valid driver license may operate one without a special examination.
What it does not exempt you from: the helmet requirement still applies to mopeds under RCW 46.37.530, and mopeds require registration. Mopeds also may not be operated on a bicycle path or trail, bikeway, equestrian trail, or hiking or recreational trail.
The 50cc scooter trap
Dealers sell a lot of machines marketed as "50cc scooters" that are not mopeds under Washington law, usually because the actual top speed exceeds 30 mph. Some are 49cc but geared to do 40. Some are sold as 50cc and are closer to 80.
The DOL frames it simply: if the speedometer reads faster than 30 mph, you need an endorsement. If you are buying used and the seller assures you no license is needed, that assurance is worth nothing at the roadside. Check the displacement plate and be honest about the speed.
Motor-driven cycles, the middle category
Between moped and full motorcycle sits a third class. RCW 46.04.332 defines a motor-driven cycle as every motorcycle, including every motor scooter, with a motor producing not more than five brake horsepower. It expressly excludes mopeds, power wheelchairs, motorized foot scooters and mobility devices.
Motor-driven cycles do require an endorsement. They also carry an odd extra restriction: they may not be operated above thirty-five miles per hour at night unless the headlamp is adequate to reveal a person or vehicle at three hundred feet.
One more consequence worth knowing: motor-driven cycles and mopeds are exempt from the mandatory liability insurance requirement, whereas motorcycles are not. See the insurance rules.
The honest safety note
A scooter is not a gentler motorcycle. It is a vehicle doing 30 mph in traffic designed for 45, with small wheels that cope badly with the potholes and expansion joints that a larger bike absorbs, and with the same complete absence of a metal cage around you.
Riders who step up from a scooter to a real motorcycle usually find the bigger machine easier, not harder: better brakes, better tyres, more stable at speed. If you are on a scooter because a motorcycle seemed intimidating, that instinct may be backwards.