Municipal streets are hereby divided into six 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 two categories: Extensions of rural expressways and some additional routes which serve very high volumes of local traffic within urban areas;
(3) Major arterial, which shall generally consist of extensions of the rural major arterials which provide continuous service through municipalities for long-distance rural travel. They are the arterial streets used to transport products into and out of municipalities;
(4) Other arterial, which shall consist of two categories: Municipal extensions of rural other arterials, and arterial movements peculiar to a municipality's own complex, that is streets which interconnect major areas of activity within a municipality, such as shopping centers, the central business district, manufacturing centers, and industrial parks;
(5) Collector, which shall consist of a group of streets which collect traffic from residential streets and move it to smaller commercial centers or to higher arterial systems; and
(6) Local, which shall consist of the balance of streets in each municipality, principally residential access service streets and local business streets. They are characterized by very short trip lengths, almost exclusively limited to vehicles desiring to go to or from an adjacent property.