Ohio authorities define a moped as not being capable of going above 20 miles per hour--otherwise, it's considered a motorcycle. Speed limits on Ohio freeways range from 55 to 65 miles per hour, and police can write tickets for driving at an "unreasonably slow speed." A moped on a freeway would be considered unreasonably slow.
Driving a moped on the freeway will likely result in a minor misdemeanor for unreasonably slow driving (basically, a traffic ticket) under state law. It is punishable by a fine of up to $150. Driving too slowly on the freeway in any type of vehicle is dangerous and should be avoided.
To drive a moped in Ohio, the Ohio Bureau of Motor Vehicles says you must be licensed and follow the law, just like any other driver. Mopeds need to have a rear-view mirror and must be registered for a license plate.