All new streets and roads shall be classified as “local” streets as defined by the Virginia Department of Transportation and, for the purposes of this chapter, shall be further classified according to their function and the projected average daily traffic (ADT). Average daily traffic shall include all traffic projected to result from the complete development of land served by the subject street, including both internal and external trips. The trip generation rates contained in the most current edition of the Trip Generation Manual (Institute of Transportation Engineers, (shall be used to determine the projected ADT. The classification based on ADT shall take precedence over the functional de-scription for purposes of determining street geometrics.

      (1) Access street: carries only the volume of traffic generated on the street itself.

     (2) Subcollector street: may carry the volume of at least one access street in addition to its own volume.

     (3) Collector street: unsuitable for providing direct residential lot access, however, occasionally no suitable alternative exists.

     (4) Arterial street: direct residential lot access is prohibited and commercial or industrial lot access is controlled and limited to high trip volume generators.

(c) Existing streets. Where existing streets which are not otherwise classified by the comprehensive plan abut or affect the design of a proposed subdivision, such existing streets shall be classified in accordance with the functional and traffic volume descriptions contained in this chapter.