This datalayer displays the Type A class roads thoughout the District of Columbia. Feature Class A roads include: Primary roads with limited access (interstate highways, toll highways); Primary roads without limited access (US highways, some state highways and county highways that connect cities and larger towns); regional and state highways state highways, Secondary and connecting roads (includes mostly state highways, but may include some county highways that connect smaller towns, subdivisions, and neighborhoods); Local, neighborhood, and rural roads, city streets, and vehicular trails.
According to the TIGER95 Data Dictionary, the definition of a divided highway has been the source of considerable discussion. Earlier specifications have defined a divided road as having, "..opposing traffic lanes that are physically separated by a median strip no less than 70 feet wide in former GBF/DIME areas or no less than 200 feet wide in non-GBF/DIME areas." This definition caused confusion in the proper coding of interstates having narrow medians. To clarify the situation, the Census Bureau now uses the term divided to refer to a road with opposing traffic lanes separated by any size median, and separated to refer to lanes that are represented in the Census TIGER? data base as two distinct complete chains. Earlier operations may have depicted widely separated lanes as a single line in the data base or created separate lines when the median was small, depending on the available source used during the update.
Road types possibly represented here are defined as follows:
-Primary Highway With Limited Access (A1): Interstate highways and some toll highways are in this category and are distinguished by the presence of interchanges. These highways are accessed by way of ramps and have multiple lanes of traffic. The opposing traffic lanes are divided by a median strip. The TIGER/Line? files may depict these opposing traffic lanes as two distinct lines in which case, the road is called separated.
-Primary Road Without Limited Access (A2): This category includes nationally and regionally important highways that do not have limited access as required by category A1. It consists mainly of US highways, but may include some state highways and county highways that connect cities and larger towns. A road in this category must be hard-surface (concrete or asphalt). It has intersections with other roads, may be divided or undivided, and have multilane or single-lane characteristics.
-Secondary and Connecting Road (A3): This category includes mostly state highways, but may include some county highways that connect smaller towns, subdivisions, and neighborhoods. The roads in this category are smaller than roads in Category A2, must be hard-surface (concrete or asphalt), and are usually undivided with single-lane characteristics. These roads usually have a local name along with a route number and intersect with many other roads and driveways.
-Local, Neighborhood, and Rural Road (A4): A road in this category is used for local traffic and usually has a single lane of traffic in each direction. In an urban area, this is a neighborhood road and street that is not a thoroughfare belonging in categories A2 or A3. In a rural area, this is a short-distance road connecting the smallest towns; the road may or may not have a state or county route number. Scenic park roads, unimproved or unpaved roads,and industrial roads are included in this category. Most roads in the Nation are classified as A4 roads.
-Vehicular Trail (A5): A road in this category is usable only by four-wheel drive vehicles, is usually a one-lane dirt trail, and is found almost exclusively in very rural areas. Sometimes the road is called a fire road or logging road and may include an abandoned railroad grade where the tracks have been removed. Minor, unpaved roads usable by ordinary cars and trucks belong in category
-Road with Special Characteristics (A6): This category includes roads, portions of a road, intersections of a road, or the ends of a road that are parts of the vehicular highway system and that have separately identifiable characteristics.
-Road as Other Thoroughfare (A7): A road in this category is not part of the vehicular highway system. It is used by bicyclists or pedestrians, and is typically inaccessible to mainstream motor traffic except for private-owner and service vehicles. This category includes foot and hiking trails located on park and forest land, as well as stairs or walkways that follow a road right-of-way and have names similar to road names.