a. Overpasses and Underpasses. On large-scale maps, overpasses and underpasses normally are shown wherever they exist. On medium-and small-scale maps they generally are shown only in open areas. An overpass is a short viaduct carrying a road or railroad above the grade of another road or railroad. An underpass is a short tunnel carrying a road or railroad below the grade of another road or railroad.
b. Bridges and Viaducts.
(1) The distinction between a bridge and a viaduct is that a bridge passes over what is predominantly water while a viaduct passes over what is predominantly land.
(2) Long bridges or viaducts are always shown. A shorter bridge or viaduct is shown if it serves as an identifiable landmark or is the only means of crossing within the general area.
(3) On long bridges or viaducts, the ends of the symbol appear in their correct locations. On shorter ones, the symbol is merely representative and the ends are not necessarily in their correct locations.
(4) Bridges and viaducts less than 20 feet long normally are not shown except when they are underpasses or overpasses.
(5) When a bridge is used to carry both a road and a railroad on either the same or different levels, the feature is shown by the road-bridge symbol with the railroad shown to the bridge ends. The symbol is labeled "Road and railroad".
(6) Footbridges are shown only in areas of sparse culture.
c. Drawbridges.
(1) Drawbridges are structures of which either the whole or part can be raised, lowered, pivoted, or turned aside to allow or to interrupt traffic.
(2) On large-scale maps, the small circle of the symbol is centered on the true location of the center of the movable part of the bridge.
d. Ferries.
(1) Ferries capable of carrying vehicular or railroad traffic normally are shown wherever they exist.
(2) Ferries for pedestrians are shown only in areas of sparse culture or where they provide the only means of water-crossing in the general area.
(3) The dashed line connects the points between which the ferry operates, without regard for the actual navigating course of the ferry.
(4) Steamship lines are not shown.
e. Fords. Fords are shown only in areas of sparse culture or where they provide the only means of water-crossing in the general area.
f. Symbols. The following contain the approved symbols for features related to communications.
