Land areas are classified by their use, as well as according to what happens on them either naturally or as a result of human activity. A certain area can belong to only one land use category. The use of an area refers to its actual use for some purpose, not to its potential or planned use. The mode of use is determined by the only or the principal use of the site or such use that excludes all other modes of use.
The site to be classified must have a surface area. Thus, a point-form site or a site with a small area is not taken into account or classified.
The land use category is determined by the primary (principal) use or the economically most important mode of land use. Structures or modes of land use underneath the surface of land are not considered when determining the land use category. Thus, a bomb shelter built inside a rock does not determine the use category of the area "above" it, and a road or railroad inside a tunnel is not a traffic area.