What's new in ArcGIS Network Analyst extension at 10.1
Hierarchical service areas
The time to generate a service area was drastically reduced in ArcGIS 10.1 because service areas now support using the hierarchy of a network dataset as they solve. This diminishes the number of roads that must be searched in the solve process and therefore makes solving a service area layer much faster.
The Location-Allocation solver, which was introduced in ArcGIS 10, included six problem types for minimizing facilities, maximizing market share, and so on. At ArcGIS 10.1, a new problem type is added: Maximize Capacitated Coverage. This problem type is ideal for choosing facility locations when space or supply is limited and relevant to what is being provided by the facilities. You can use Maximize Capacitated Coverage to better locate hospitals with a given number of beds, schools with a limited student occupancy, and warehouses with allotted storage space for inventory.
Restrictions: Prohibit, Avoid, and Prefer
Previously, using a restriction on a network element allowed you to prohibit traversal on it. At 10.1, restrictions were expanded to allow you to prohibit, avoid, or even prefer network elements.
Prohibiting elements allows you to model one-way streets, illegal turns, weight limits, and so on.
Avoiding elements means Network Analyst will try to detour around network elements that use the restriction, but only if doing so isn't too far or if traveling on the restricted element isn't required. For instance, you might want to avoid toll roads as long as that doesn't cause you to go too far out of your way.
Preferring elements makes them more attractive to a solver. For example, you might want to prefer designated hazardous-materials roads when routing trucks that are carrying hazmats. Similarly, you can create routes for bicycles that prefer bike paths and roads with bike lanes. (Of course you can mix the various kinds of restrictions to model your mode of transportation, for instance, you can prefer bike lanes and bike paths but prohibit Interstate highways.)
To support this functionality, all restriction attributes are assigned a Restriction Usage parameter, which allows you to choose whether to prohibit, avoid, or prefer network elements that use the restriction. If you want to avoid or prefer elements, you can specify the degree to which they are avoided or preferred.
Live traffic data
Network datasets created with ArcGIS 10.1 can incorporate live traffic data, which makes it possible to:
- Visualize current traffic conditions on a map
- Solve any network analysis using live travel speeds
The live traffic model builds on the historical traffic model, which was released with 10.0. Historical traffic provides travel times that vary depending on the time of day and day of the week. The times are based on historical averages. Performing a network analysis using historical traffic data returns more accurate results than those returned using a simple, static cost attribute.
Live traffic fills in where the historical traffic model falls short: accounting for current traffic conditions. When you solve a network analysis based on the current time, using live traffic will tend to improve results, even over those created using historical traffic.
Update Traffic Data geoprocessing tool
This tool was added to support the live traffic model. It downloads live traffic data from a data provider's web service and stores the data in a file format that network datasets can read. You set up this tool to periodically download data and create dynamic traffic format (DTF) files and configure a network dataset to reference these files via a UNC path or HTTP endpoint.
Update Traffic Incidents geoprocessing tool
This tool downloads traffic incidents, such as vehicle accidents and construction work, from a data provider and creates a point feature class of the incidents. Overlaying incidents on a map of live traffic provides insight into why travel speeds are slower than normal. This tool is typically configured to write to an enterprise geodatabase so that the incidents can be viewed or shared as a map or feature service while still being periodically updated.
Support for traffic data in all solvers
In 10.0, historical traffic was introduced, but it was supported by just two of the six solvers: Route and Vehicle Routing Problem. Now all solvers support traffic data. Furthermore, they all support live traffic along with historical traffic.
To use traffic data, you choose a time-enabled cost attribute and set a start time for the analysis layer.
The Network Analyst module (Python)
The Network Analyst module is a Python module that provides access to all of the geoprocessing tools available in the Network Analyst toolbox as well as helper functions and classes. You can use this module with other ArcPy modules to automate workflows using Python.
Support for Python scripts in evaluators
Previously, the field and VBScript evaluators only supported VBScript. These two evaluators were enhanced for ArcGIS 10.1 to also support scripts written in Python. Accordingly, VBScript evaluators are now referred to as script evaluators.
Copy Traversed Source Features geoprocessing tool
This geoprocessing tool creates feature classes containing the edges, junctions, and turns that a solved network analysis layer traversed.
After performing a network analysis, you might want to study some aspect of the underlying network using this tool. For example, once you have generated several routes in a study area, you can use Copy Traversed Source Feature to help you determine the number of times a particular street segment was traversed.
Better support for loading moving vehicles into an analysis layer
Loading network locations into a network analysis layer can account for the bearing and bearing tolerance of the input points so that they placed more accurately on the network. This feature is especially useful when loading GPS data from moving vehicles.
In the illustration below, the gray triangle to the left marks a vehicle's location and its bearing as captured by a GPS receiver. Clearly, the location and bearing were somewhat inaccurate. If bearing was ignored, the point would be located on the east–west edge since that is closest to the gray triangle; however, by snapping the triangle to edges and comparing the bearing with a bearing tolerance, it is clear that the point should be located on the north–south street heading to the north.
Many kinds of network analyses push the limits of the computer resources due to the sheer quantity of network elements and attribute values that are processed. Because ArcGIS Server is a true 64-bit application at 10.1, the limits have been raised significantly, and now it is possible to solve much larger network analyses using ArcGIS Server.
Generate Service Areas geoprocessing tool
ArcGIS 10.0 and prior versions allowed you to create web services that solved service area problems; however, the new Generate Service Areas geoprocessing tool simplifies and streamlines this process.
Prior to 10.1, you needed to add the Make Service Area Layer tool to a model, know which other geoprocessing tools to add to the model, and know the proper sequence in which to link them. Now you need to add one tool only, Generate Service Areas, choose which parameters to expose, then publish the model. The inputs for Generate Service Areas are feature sets, and the outputs are feature classes; these formats simplify managing the input and output data in a web environment.
Note that you should continue to use Make Service Area Layer when working within ArcGIS for Desktop only.
Solve Vehicle Routing Problem geoprocessing tool
A new VRP tool, Solve Vehicle Routing Problem, is included with ArcGIS Network Analyst 10.1 to facilitate the process of authoring, publishing, and managing data for VRP web services. It should be used for ArcGIS Server instead of a model that includes Make Vehicle Routing Problem.
Similar to the benefits of Generate Service Areas over Make Service Area Layer, Solve Vehicle Routing Problem lets you configure and publish a model containing a single tool. Also, the inputs and outputs of the new tool are feature sets and feature classes, which make handling the web service's data simpler.
Note that Make Vehicle Routing Problem is still the tool of choice when creating network analysis layers for use outside of ArcGIS for Server.