Editing Transport network analysis (section)

==Network data==

Network analysis requires detailed data representing the elements of the network and its properties.<ref>{{cite web |title=What is a network dataset? |url=https://pro.arcgis.com/en/pro-app/latest/help/analysis/networks/what-is-network-dataset-.htm |website=ArcGIS Pro Documentation |publisher=Esri}}</ref> The core of a network dataset is a [[Vector graphics|vector]] layer of polylines representing the paths of travel, either precise geographic routes or schematic diagrams, known as ''edges''. In addition, information is needed on the [[network topology]], representing the connections between the lines, thus enabling the transport from one line to another to be modeled. Typically, these connection points, or ''nodes'', are included as an additional dataset.<ref>{{cite web |title=Network elements |url=https://pro.arcgis.com/en/pro-app/latest/help/analysis/networks/network-elements.htm |website=ArcGIS Pro Documentation |publisher=Esri |access-date=17 March 2021}}</ref>

Both the edges and nodes are attributed with properties related to the movement or flow:
* ''Capacity'', measurements of any limitation on the volume of flow allowed, such as the number of lanes in a road, telecommunications bandwidth, or pipe diameter.
* ''Impedance'', measurements of any resistance to flow or to the speed of flow, such as a speed limit or a forbidden turn direction at a street intersection
* ''Cost'' accumulated through individual travel along the edge or through the node, commonly elapsed time, in keeping with the principle of [[friction of distance]]. For example, a node in a street network may require a different amount of time to make a particular left turn or right turn. Such costs can vary over time, such as the pattern of travel time along an urban street depending on diurnal cycles of traffic volume.
* ''Flow volume'', measurements of the actual movement taking place. This may be specific time-encoded measurements collected using [[sensor network]]s such as [[traffic counter]]s, or general trends over a period of time, such as [[Annual average daily traffic]] (AADT).