ArcGIS Network Analyst

ArcGIS Network Analyst is an extension to Esri's ArcGIS for Desktop product suite that provides spatial analysis on a transportation network such as routing, fleet routing, travel directions, closest facility, service area, and location-allocation. With ArcGIS Network Analyst, users can create applications using a network dataset to build multimodal routes, provide travel directions, look for closest facilities, and create service areas and origin-destination cost matrices.

Features
ArcGIS Network Analyst helps to dynamically model realistic network conditions and solve vehicle routing problems in a transportation system that include turn restrictions, speed limits, height restrictions, and traffic conditions at different times of the day.

With ArcGIS Network Analyst, users can perform:
 * Drive-time analysis
 * Point-to-point routing
 * Fleet routing
 * Route directions
 * Service area definition
 * Shortest path analysis
 * Optimum route analysis
 * Closest facility analysis
 * Origin-destination analysis

The origin-destination cost matrices that the ArcGIS Network Analyst extension creates is often used for larger analyses. For example, predicting travel behavior incorporates the distances people would need to travel to reach certain attractions. These network distances are applied in mathematical expressions to help make trip forecasts. With that, users are able to reduce transportation costs by optimally sequencing stops and finding the shortest paths between the stops while considering several constraints such as time windows, vehicle capacities, and maximum travel times. Users are also able to improve customer satisfaction with quicker response times or by providing more convenient facility locations.

System Requirements
The system requirements for ArcGIS Network Analyst are determined by user's existing product version and platform configuration.
 * ArcGIS Network Analyst requires ArcGIS for Desktop (Basic, Standard, or Advanced).
 * The ArcGIS Network Analyst extension is also available for ArcGIS Engine and ArcGIS for Server.
 * A separate ArcGIS Network Analyst extension license is required for each application.

Refer to the ArcGIS 10.1 for Desktop system requirements for more information.

Network models in ArcGIS Network Analyst
A network is a system of interconnected elements such as edges (lines) and connecting junctions (points) that represent possible routes from one location to another. The ArcGIS Network Analyst extension is used to analyze these networks, with the most common network analysis being finding the shortest path between two points. ArcGIS groups networks into two categories: geometric networks and network datasets. Geometric networks consist of river networks and utility networks like electrical, gas, sewer, and water lines that allow travel on edges in only one direction at a time, where the path is determined by external forces like gravity, electromagnetism, and water pressure.

A network dataset is created from source features, which include simple features (lines and points) and turns, and store the connectivity of the source features. A network dataset is used to model a single mode of transportation, like roads, or a complex multimodal network made up of several transportation modes like roads, railroads, and waterways. Three-dimensional network datasets are used to model the interior pathways of buildings, mines, caves, and such. The ArcGIS Network Analyst extension can also read Smart Data Compression (SDC) network datasets that allows users to perform network analysis on vendor-supplied SDC data, without having to create user's own network dataset.

Users can create and maintain network datasets in shapefile, personal geodatabase, and enterprise geodatabase formats. But a network dataset is best created from feature classes in a feature dataset of a geodatabase. Since a feature dataset can store and easily communicate with multiple feature classes, the network dataset can support multiple sources and is used to model multimodal networks. The shapefile-based network dataset provides ArcView users with the opportunity to rapidly migrate their data and is created from a polyline shapefile containing the network source or a shapefile turn feature class, but it cannot support multiple edge sources and cannot be used to model multimodal networks.