Roads

Road edges are defined as the edge of the improved surface including the improved shoulder but do not include the unimproved shoulder, only the travel part of the road. The road network is compiled to include all open intersections. Features do not overlap sidewalks, but have the sidewalk area cut out of the road polygons. Overlapping features are acceptable if one of the features is hidden. Road: A generally named thoroughfare, that is usually paved and can be public or private. Unimproved thoroughfares are excluded. Road polygons are formed by a combination of road edge, curb, sidewalk, street intersection closure line, and map sheet edge. Paved Median Island: Perimeter of non-traffic paved areas that separate traffic lanes in opposing directions. Unpaved Median Island: Perimeter of non-traffic grassy, unpaved areas that separate traffic lanes in opposing directions. Paved Traffic Island: Perimeter of non-traffic concrete areas in the middle of streets designed to segregate traffic flow. This does not include linear barriers, e.g., Jersey barriers, walls or guardrails, or point barriers, such as impact attenuators. Features do not overlap sidewalks. Unpaved Traffic Island: Perimeter of non-traffic unpaved, grassy areas in the middle of streets designed to segregate traffic flow. This does not include linear barriers, e.g., Jersey barriers, walls or guardrails, or point barriers, such as impact attenuators. Features do not overlap sidewalks. Alley: Perimeter of alleys first plotted photogrammetrically from other indicators such as building footprints, fence lines, curb lines, walls, paved or unpaved drives, and map sheet edge. Alley polygons are closed along the lines where they intersect with road polygons. Paved Drive: A paved driveway for a building or entranceway for a parking lot. Driveways are neither streets nor alleys, but provide access to public facilities, such as a drive to a monument, museum, hotel, large estate, sports field or golf course, grounds of the U.S. Capitol, etc. If a driveway is less than 200 feet and leads to a parking lot, the entire paved area is captured as Parking Lot. Driveways are photogrammetrically compiled as polygons and not compiled from individual vectors on different levels. Parking Lot: Generally paved surfaces used for cars to park on. Paved drives usually form entrances to these features, if the drive is more than 200 feet. If the driveway is less than 200 feet leading into the parking lot, the entire paved area is captured as Parking Lot. Parking lots sharing a common boundary with linear features must have the common segment captured once, but coded as both polygon and line. Small parking areas, where individuals park their cars in the middle of a block off a public alley, are not captured as parking lots. These are either public space (e.g., alleys) or private space where owners permit parking to occur. Intersection: A location where more than one road comes together. For standard cross streets, intersection polygons are bounded by curbs and four closure lines at street intersection crosswalks (outer line) or placed arbitrarily where crosswalks could logically be placed. For "T" intersections, the polygons are bounded by curbs and three such closure lines. Complex intersections can have more closure lines. Entire traffic circles are coded as intersections. Hidden Road: A section of a road that passes underneath a bridge or overpass and is not visible in an aerial photograph, but the location can be interpreted based on the road on either side of the bridge. Hidden Median: A road median that exists underneath a bridge or overpass and is not fully visible in an aerial photograph, but the location can be interpreted based on the information visible on either side of the bridge.道路边缘（Road edge）定义为经铺装的路面边缘，包含改良式路肩，但不包含未改良路肩，仅涵盖道路的通行区域。 道路网络（road network）在编制时需纳入所有开放交叉口。 地理要素不得与人行道重叠，需从道路多边形（road polygon）中扣除人行道区域。若其中一个要素处于隐藏状态，则要素重叠是允许的。 道路（Road）：指通常已铺装、可公有或私有的、一般有命名的通行干道，未经过铺装改良的通行干道除外。 道路多边形（road polygon）由道路边缘、路缘石（curb）、人行道、交叉口闭合线以及图廓边共同构成。 铺装式中央分隔带（Paved Median Island）：分隔对向行车道的非通行铺装区域的周长边界。 非铺装式中央分隔带（Unpaved Median Island）：分隔对向行车道的非通行草地、非铺装区域的周长边界。 铺装式交通岛（Paved Traffic Island）：设置于街道中央、用于分隔车流的非通行混凝土区域的周长边界，不包含线性障碍物（如泽西护栏、墙体或护栏）以及点状障碍物（如防撞缓冲装置）。该地理要素不得与人行道重叠。 非铺装式交通岛（Unpaved Traffic Island）：设置于街道中央、用于分隔车流的非通行非铺装草地区域的周长边界，不包含线性障碍物（如泽西护栏、墙体或护栏）以及点状障碍物（如防撞缓冲装置）。该地理要素不得与人行道重叠。 小巷（Alley）：指通过摄影测量方式，基于建筑基底（building footprints）、围栏线、路缘线、墙体、铺装或非铺装车道以及图廓边等要素首次绘出的小巷的周长边界。小巷多边形（alley polygon）在与道路多边形相交的沿线处保持闭合。 铺装车道（Paved Drive）：指用于建筑物或停车场入口的铺装车道。车道既不属于街道也不属于小巷，而是用于通往公共设施的通路，例如通往纪念碑、博物馆、酒店、大型庄园、运动场、高尔夫球场或美国国会大厦园区等的车道。若某条车道长度小于200英尺且通往停车场，则其整个铺装区域将被作为停车场（Parking Lot）进行采集。车道通过摄影测量方式以多边形形式编制，而非基于不同层级的单个矢量进行采集。 停车场（Parking Lot）：指供车辆停放的一般为铺装的地面。若车道长度超过200英尺，则铺装车道通常作为此类要素的入口。若通往停车场的车道长度小于200英尺，则其整个铺装区域将被作为停车场进行采集。与线性要素共享边界的停车场，其公共边界段仅需采集一次，但需同时编码为多边形与线要素。个体在街区中央公共小巷旁停车的小型停车区域，不得作为停车场进行采集，此类区域要么属于公共空间（如小巷），要么属于业主允许停车的私人空间。 交叉口（Intersection）：指两条及以上道路交汇的位置。对于标准十字交叉口，交叉口多边形由路缘石以及交叉口人行横道（外线）处的四条闭合线界定，或在人行横道合理存在的位置任意设置。对于“T”型交叉口，多边形由路缘石以及三条此类闭合线界定。复杂交叉口可包含更多闭合线。整个环岛（traffic circle）均被编码为交叉口。 隐藏道路（Hidden Road）：指位于桥梁或立交桥下方、在航空影像中不可见，但可基于桥梁两侧的道路推断其位置的道路路段。 隐藏式中央分隔带（Hidden Median）：指位于桥梁或立交桥下方、在航空影像中未完全显现，但可基于桥梁两侧的可见信息推断其位置的道路中央分隔带。