It is hereby declared that any expressway, turnpike, feeder road, state local service road or park and forest road or other road, or any subsequent expressway, turnpike feeder road, state local service road, park and forest road or other road constructed pursuant to this article shall be a part of the state road system, although subject to the provisions of this article and of any bonds or trust agreements entered into pursuant thereto, and that the construction of such parkway projects shall be considered as developments of the state road system.