You can ride a derbi gpr50r as a moped beacuse it comes with arestrictor plate in the exhaust which limits the amount of exhaust gases that can escape from the engine. This limits the power the engine produces and so it should not go over about 35mph restricted. Then once you have bought it you take the plate out (easy to find) and voila! your "moped" will do about 55mph. Cool huh it's just a bit illegal but who cares unless the cops take off your exhaust and examine it. In short buy one because their great fun and legal if restricted. I should know I have one!