Rural highways are hereby divided into nine functional classifications as follows:

(1) Interstate, which shall consist of the federally designated National System of Interstate and Defense Highways;

(2) Expressway, which shall consist of a group of highways following major traffic desires in Nebraska which rank next in importance to the National System of Interstate and Defense Highways. The expressway system is one which ultimately should be developed to multilane divided highway standards;

(3) Major arterial, which shall consist of the balance of routes which serve major statewide interests for highway transportation. This includes super-two, which shall consist of two-lane highways designed primarily for through traffic with passing lanes spaced intermittently and on alternating sides of the highway to provide predictable opportunities to pass slower moving vehicles. This system is characterized by high-speed, relatively long-distance travel patterns;

(4) Scenic-recreation, which shall consist of highways or roads located within or which provide access to or through state parks, recreation or wilderness areas, other areas of geographical, historical, geological, recreational, biological, or archaeological significance, or areas of scenic beauty;

(5) Other arterial, which shall consist of a group of highways of less importance as through-travel routes which would serve places of smaller population and smaller recreation areas not served by the higher systems;

(6) Collector, which shall consist of a group of highways which pick up traffic from many local or land-service roads and carry it to community centers or to the arterial systems. They are the main school bus routes, mail routes, and farm-to-market routes;

(7) Local, which shall consist of all remaining rural roads, except minimum maintenance roads and remote residential roads;

(8) Minimum maintenance, which shall consist of (a) roads used occasionally by a limited number of people as alternative access roads for areas served primarily by local, collector, or arterial roads or (b) roads which are the principal access roads to agricultural lands for farm machinery and which are not primarily used by passenger or commercial vehicles; and

(9) Remote residential, which shall consist of roads or segments of roads in remote areas of counties with (a) a population density of no more than five people per square mile or (b) an area of at least one thousand square miles, and which roads or segments of roads serve as primary access to no more than seven residences. For purposes of this subdivision, residence means a structure which serves as a primary residence for more than six months of a calendar year. Population shall be determined using data from the most recent federal decennial census.

The rural highways classified under subdivisions (1) through (3) of this section should, combined, serve every incorporated municipality having a minimum population of one hundred inhabitants as determined by the most recent federal decennial census or the most recent revised certified count by the United States Bureau of the Census or sufficient commerce, a part of which will be served by stubs or spurs, and along with rural highways classified under subdivision (4) of this section, should serve the major recreational areas of the state.

For purposes of this section, sufficient commerce means a minimum of two hundred thousand dollars of gross receipts under the Nebraska Revenue Act of 1967.