I have a 49cc scooter and need to know what roads are federal interstate highways.
Google is really your friend here...You are the first person I know that did not know what an expressway or freeway is though...They have divided lanes, two or three lanes or more on each side of the divider, as well as on ramps and off ramps...Click on the Google link below and read all about it.
They also have signs that look like this that say "Interstate" right on them.
Ps...Never take a moped on an Interstate highway or even a highway with speeds posted too fast for a moped to go safely, you will get killed or seriously hurt doing so...Mopeds are made for around town traveling at no more than say about 35 MPH, NOT highways.