The following meanings shall be ascribed to roads comprising the state road system:
(a) "Expressway." -- Serves major intrastate and interstate travel, including federal interstate routes.
(b) "Trunkline." -- Serves major city to city travel.
(c) "Feeder." -- Serves community to community travel or collects and feeds traffic to the higher systems or both.
(d) "State local service." -- Localized arterial and spur roads which provide land access and socioeconomic benefits to abutting properties.
(e) "Park and forest." -- Serves travel within state parks, state forests and public hunting and fishing areas.