What is a "motor driven cycle" if not a motorcycle?

I thought of this one while driving between Chicago and Champaign this weekend. I always see signs on the on ramps for interstates that say you cannot operate “motor driven cycles” on said roadways. However I always see people on motorcycles crusing along by me. Are all motorcyclists violating the law somehow, or is there a differance between your average Harley and a “motor driven cycle”?

Think moped, a motorized bicycle with a top speed around 30 MPH with a good tailwind. wouldn’t want one on an Interstate.


According to Colorado (and a lot of other states…)

So basically, Harley = Good. Moped = Bad.

Though I couldn’t find anything official from the government in a few minutes of searching, this site seems to indicate that in Illinois, a moped is a type of motor driven cycle and has the following definition:

I’m not sure what “brake horsepower” is (or how it is different from plain old “horsepower”), but it must be some measure of power. I’ve always heard motorcycle power quoted in CCs (cubic centimeters, measuring the displacement of the engine I believe?). I grew up in Michigan, and IIRC, the signs on the highway on-ramps specifically said something like “no motorcycles under 125 cubic centimeters”.

From http://dictionary.reference.com/search?q=brake+horsepower&r=67 : “The actual or useful horsepower of an engine, usually determined from the force exerted on a friction brake or dynamometer connected to the drive shaft.”

CC does stand for cubic centimeters, and it is a measure of the engine displacement (the combined volume of the cylinders). It is not a measure of power, although obviously the bigger the engine the more power it can produce.

I give you the Danish knallert - a moter driven cycle if ever I saw one.

Two common criteria for non-motorcycle er, motor-cycles, is an engine displacement of less than 50cc, and, in some cases, they must have pedals. This is why mopeds have pedals. Heh.