What is Network Analyst?

With the ArcGIS Network Analyst extension, you can answer questions like the following:

• What is the quickest way to get from point A to point B?
• Which houses are within five minutes of a fire station?
• What market areas does a business cover?

  The green points represent warehouses in various cities, and the polygons represent their market areas, which are divided into three rings. The surrounding green polygons can be reached by trucks within two hours; orange, within four hours; and red, within six hours.

• A person wants to visit a store. Which branch should the potential customer visit to minimize travel time?
• Which ambulances or patrol cars can respond quickest to an incident?

  The nearest police cruisers are assigned to incidents. The number of police officers needed at each location depends on the severity of the incident. Routes and expected response times for each car are generated.

• How can a fleet of delivery or service vehicles improve customer service and minimize transportation costs?

  Three food delivery trucks at a distribution center are assigned grocery stores and routes to the stores that minimize transportation costs. Vehicle capacities, lunch breaks, and maximum travel time constraints are included in the analysis.

• Where can a business open a store to maximize market share?
• If a company has to downsize, which stores should it close to maintain the most overall demand?

Businesses, public services, and other organizations benefit from Network Analyst because it helps them run their operations more efficiently and make better strategic decisions. These organizations can better understand dynamic markets, both current and potential, once they know who can access their goods or services. Transportation costs can be reduced 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. Customer service can be improved through quicker response times or more convenient facility locations. Network Analyst facilitates understanding and solving problems of this nature.

Researchers and analysts commonly benefit from the Network Analyst ability to determine the least-cost network paths between several origins and destinations. The origin-destination cost matrices that Network Analyst creates often become input for larger analyses. For instance, predicting travel behavior frequently 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.

The OD cost matrix analysis calculates the least-cost network paths from origins to destinations. It outputs line features that link origins to destinations. Each line feature stores the total network cost of the trip as an attribute value. Analysts often take the attribute table and use it as input for linear programming applications.

Similarly, some analyses in spatial statistics provide more accurate results when network distances are used in place of straight-line distances. Consider as an example traffic-incident analysis, which has the aim of locating clusters of traffic accidents, pinpointing their causes, and taking action to reduce the number of accidents. Since cars travel on roads, determining clusters of car accidents with network distances is far more effective than using straight-line distances.

Before you can perform network analyses to answer questions like those listed above, you need a network dataset, which models a transportation network.

What is a network?

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.

People, resources, and goods tend to travel along networks: cars and trucks travel on roads, airliners fly on predetermined flight paths, oil flows in pipelines. By modeling potential travel paths with a network, it is possible to perform analyses related to the movement of the oil, trucks, or other agents on the network. The most common network analysis is finding the shortest path between two points.

ArcGIS groups networks into two categories: geometric networks and network datasets.

Geometric networks (utility and river networks)

River networks and utility networks—like electrical, gas, sewer, and water lines—allow travel on edges in only one direction at a time. The agent in the network—for instance, the oil flowing in a pipeline—can't choose which direction to travel; rather, the path it takes is determined by external forces: gravity, electromagnetism, water pressure, and so on. An engineer can control the flow of the agent by controlling how external forces act on the agent.

Note:

In ArcGIS, utility and river networks are best modeled by geometric networks.

River networks and utility networks, such as a pipeline, are best modeled in ArcGIS using geometric networks, which don't require an ArcGIS Network Analyst extension.

Network datasets (transportation networks)

Transportation networks—like street, pedestrian, and railroad networks—can allow travel on edges in both directions. The agent on the network—for instance, a truck driver traveling on roads—is generally free to decide the direction of traversal as well as the destination.

Note:

In ArcGIS, transportation networks are best modeled by network datasets.

License:

The ArcGIS Network Analyst extension is required to create and edit network datasets.

Transportation networks, such as roads, are best modeled in ArcGIS by network datasets. Working with network datasets and performing analyses on them requires the ArcGIS Network Analyst extension.

Multimodal network datasets

A network dataset is capable of modeling a single mode of transportation, like roads, or a multimodal network made up of several transportation modes like roads, railroads, and waterways.

A least-cost route is shown for a pedestrian who can walk along the street network and ride on the subway network.

3D network datasets

Three-dimensional network datasets enable you to model the interior pathways of buildings, mines, caves, and so on.

A quickest route connects a stop on the first floor of a building to one on the third floor. Using restrictions, you can perform analyses that avoid staircases for wheelchair-accessible routes or that avoid elevators for evacuation planning.

If you have street features with accurate z-coordinate values, you can use them with z-aware features that model pathways inside buildings to create 3D networks of campuses or even cities. This allows you to answer questions like the following:

• What is the best wheelchair-accessible route between rooms in different buildings?
• What floors of a high-rise building can't be reached by a fire department within eight minutes?