ClosestFacilitySolverProperties

Summary

Provides access to analysis properties from a closest facility network analysis layer. The GetSolverProperties function is used to obtain a ClosestFacilitySolverProperties object from a closest facility network analysis layer.

Discussion

The ClosestFacilitySolverProperties object provides read and write access to all the analysis properties of a closest facility network analysis layer. The object can be used to modify the desired analysis properties of the closest facility layer, and the corresponding layer can be re-solved to determine the appropriate results. A new closest facility layer can be created using the Make Closest Facility Layer geoprocessing tool. Obtaining the ClosestFacilitySolverProperties object from a new closest facility layer allows you to reuse the existing layer for subsequent analyses rather than create a new layer for each analysis, which can be slow.

After modifying the properties on the ClosestFacilitySolverProperties object, the corresponding layer can be immediately used with other functions and geoprocessing tools. There is no refresh or update of the layer required to honor the changes modified through the object.

Properties

Property	Explanation	Data Type
accumulators (Read and Write)	Provides the ability to get or set a list of network cost attributes that are accumulated as part of the analysis. An empty list, [], indicates that no cost attributes are accumulated.	String
attributeParameters (Read and Write)	Provides the ability to get or set the parameterized attributes to be used in the analysis. The property returns a Python dictionary. The dictionary key is a two-value tuple consisting of the attribute name and the parameter name. The value for each item in the dictionary is the parameter value. Parameterized network attributes are used to model some dynamic aspect of an attribute's value. For example, a tunnel with a height restriction of 12 feet can be modeled using a parameter. In this case, the vehicle's height in feet should be specified as the parameter value. If the vehicle is taller than 12 feet, this restriction will then evaluate to True, thereby restricting travel through the tunnel. Similarly, a bridge could have a parameter to specify a weight restriction. Attempting to modify the attributeParameters property in place won't result in updated values. Instead, you should always use a new dictionary object to set values for the property. The following two code blocks demonstrate the difference between these two approaches. #Don't attempt to modify the attributeParameters property in place. #This coding method won't work. solverProps.attributeParameters[('HeightRestriction', 'RestrictionUsage')] = "PROHIBITED" #Modify the attributeParameters property using a new dictionary object. #This coding method works. params = solverProps.attributeParameters params[('HeightRestriction', 'RestrictionUsage')] = "PROHIBITED" solverProps.attributeParameters = params If the network analysis layer does not have parameterized attributes, this property returns None.	Dictionary
defaultCutoff (Read and Write)	Provides the ability to get or set the default impedance value at which the solver will stop searching for facilities for a given incident. A value of None is used to specify that no cutoff should be used.	Double
defaultTargetFacilityCount (Read and Write)	Provides the ability to get or set the number of closest facilities to find per incident.	Integer
impedance (Read and Write)	Provides the ability to get or set the network cost attribute used as impedance. This cost attribute is minimized while determining the closest facility and the best route to the closest facility.	String
outputPathShape (Read and Write)	Provides the ability to get or set the shape type for the route features that are output by the solver. The following is a list of possible values: TRUE_LINES_WITH_MEASURES —The output routes will have the exact shape of the underlying network sources. Furthermore, the output includes route measurements for linear referencing. The measurements increase from the first stop and record the cumulative impedance to reach a given position. TRUE_LINES_WITHOUT_MEASURES —The output routes will have the exact shape of the underlying network sources. STRAIGHT_LINES —The output route shape will be a single straight line between each of the incident-facility pair. NO_LINES —No shape will be generated for the output routes.	String
restrictions (Read and Write)	Provides the ability to get or set a list of restriction attributes that are applied for the analysis. An empty list, [], indicates that no restriction attributes are used for the analysis.	String
solverName (Read Only)	Returns the name of the solver being referenced by the Network Analyst layer used to obtain the solver properties object. The property always returns the string value Closest Facility Solver when accessed from a ClosestFacilitySolverProperties object.	String
streetDirectionsProperties (Read and Write)	Provides read and write access to StreetDirectionsProperties, allowing you to customize the directions output from your closest facility layer.	Object
timeOfDay (Read and Write)	Provides the ability to get or set the time and date at which the routes should begin or end. The interpretation of this value depends on whether timeOfDayUsage property is set to START_TIME or END_TIME. A value of None can be used to specify that no date and time should be used. Instead of using a particular date, a day of the week can be specified using the following dates. Today—12/30/1899 Sunday—12/31/1899 Monday—1/1/1900 Tuesday—1/2/1900 Wednesday—1/3/1900 Thursday—1/4/1900 Friday—1/5/1900 Saturday—1/6/1900 For example, to specify that the route should start or end at 8:00 a.m. on Monday, specify the value as datetime.datetime(1900, 1, 1, 8,0,0). The timeZoneUsage parameter specifies whether the date and time refer to UTC or the time zone in which the facilities or incidents are located.	DateTime
timeOfDayUsage (Read and Write)	Controls whether the value of the timeOfDay property represents the arrival or departure times for the routes. The following is a list of possible values: END_TIME —The routes arrive at the facilities or incidents at the time you set in the timeOfDay property. This choice is useful if arrival time is more important; that is, you want to know what time you need to leave in order to arrive at your destination at a given time. START_TIME —The routes depart from the facilities or incidents at the time you set in the timeOfDay property. This choice is useful to find the best routes given a departure time. NOT_USED —The routes do not use a start or end time and date. This choice should be used if the timeOfDay property has a value of None.	String
timeZoneUsage (Read and Write)	Specifies the time zone of the timeOfDay parameter. GEO_LOCAL —The timeOfDay parameter refers to the time zone in which the facilities or incidents are located. If timeOfDayUsage is set to Start_Time and travelDirection is TRAVEL_FROM, this is the time zone of the facilities. If timeOfDayUsage is set to Start_Time and travelDirection is TRAVEL_TO, this is the time zone of the incidents. If timeOfDayUsage is set to End_Time and travelDirection is TRAVEL_FROM, this is the time zone of the incidents. If timeOfDayUsage is set to End_Time and travelDirection is TRAVEL_TO, this is the time zone of the facilities. UTC —The timeOfDay parameter refers to Coordinated Universal Time (UTC). Choose this option if you want to find what's nearest for a specific time, such as now, but aren't certain in which time zone the facilities or incidents will be located. Irrespective of the timeZoneUsage setting, if your facilities and incidents are in multiple time zones, the following rules are enforced by the tool: All incidents must be in the same time zone when Specifying a start time and traveling from incident to facility Specifying an end time and traveling from facility to incident All facilities must be in the same time zone when Specifying a start time and traveling from facility to incident Specifying an end time and traveling from incident to facility	String
travelDirection (Read and Write)	Provides the ability to get or set the direction of travel between facilities and incidents during the analysis. The following is a list of possible values: TRAVEL_FROM —Direction of travel is from facilities to incidents. TRAVEL_TO —Direction of travel is from incidents to facilities.	String
useHierarchy (Read and Write)	Controls the use of the hierarchy attribute while performing the analysis. The following is a list of possible values: USE_HIERARCHY — Use the hierarchy attribute for the analysis. Using a hierarchy results in the solver preferring higher-order edges to lower-order edges. Hierarchical solves are faster, and they can be used to simulate the preference of a driver who chooses to travel on freeways over local roads when possible—even if that means a longer trip. This option is applicable only if the network dataset referenced by the Network Analyst layer has a hierarchy attribute. A value of True can also be used to specify this option. NO_HIERARCHY —Do not use the hierarchy attribute for the analysis. Not using a hierarchy yields an exact route for the network dataset. A value of False can also be used to specify this option.	String
uTurns (Read and Write)	Provides the ability to get or set the policy that indicates how the U-turns at junctions that could occur during network traversal between stops are being handled by the solver. The following is a list of possible values: ALLOW_UTURNS —U-turns are permitted at junctions with any number of connected edges. NO_UTURNS —U-turns are prohibited at all junctions, regardless of junction valency. Note, however, that U-turns are still permitted at network locations even when this setting is chosen; however, you can set the individual network locations' CurbApproach property to prohibit U-turns there as well. ALLOW_DEAD_ENDS_ONLY —U-turns are prohibited at all junctions, except those that have only one adjacent edge (a dead end). ALLOW_DEAD_ENDS_AND_INTERSECTIONS_ONLY —U-turns are prohibited at junctions where exactly two adjacent edges meet but are permitted at intersections (junctions with three or more adjacent edges) and dead ends (junctions with exactly one adjacent edge). Often, networks have extraneous junctions in the middle of road segments. This option prevents vehicles from making U-turns at these locations.	String

Method Overview

Method	Explanation
applyTravelMode (travel_mode)	Updates the analysis properties of a network analyst layer based on a travel mode object. The updated network analyst layer can then be solved to complete the analysis.

Methods

applyTravelMode (travel_mode)

Parameter	Explanation	Data Type
travel_mode	A variable that references a travel mode object derived from a network dataset. A list of travel mode objects can be obtained by calling the arcpy.na.GetTravelModes function.	Object

When a network analyst layer is created, it is assigned default values for all of its analysis properties. The individual analysis properties can be updated using a solver properties object obtained from the network analyst layer. A travel mode stores a predefined set of analysis settings that help to perform a particular analysis, such as a walking time travel mode that stores the analysis settings required to perform a time-based walking analysis.

Using the applyTravelMode method, all the analysis settings that are defined in a travel mode can be applied at once. After the analysis properties are updated, the network analyst layer can be solved to complete the analysis.

If there is an error when updating the solver properties, such as when the provided travel mode references properties that don't exist on the current network dataset or references properties that are no longer applicable to the network dataset that was used to create the network analyst layer corresponding to the solver properties object, no exceptions are raised. The method will execute successfully, but you will get errors when you try to solve such a network analyst layer.

If the travel_mode parameter does not reference a travel mode object or a string, a TypeError exception is raised. If the travel_mode parameter references a string and the string cannot be internally converted to a valid string representation of a travel mode object, a ValueError exception is raised.

Code sample

ClosestFacilitySolverProperties example 1 (Python window)

The script shows how to update a closest facility network analysis layer to find three facilities without using a cutoff value. It assumes that a closest facility layer called Closest Hospitals has been created in a new map document based on the tutorial network dataset for San Francisco region.

#Get the closest facility layer object from a layer named "Closest Hospitals" in
#the table of contents
cfLayer = arcpy.mapping.Layer("Closest Hospitals")

#Get the closest facility solver properties object from the closest facility layer
solverProps = arcpy.na.GetSolverProperties(cfLayer)

#Update the properties for the closest facility layer using the closest facility
#solver properties object
solverProps.defaultCutoff = None
solverProps.defaultTargetFacilityCount = 3

ApplyTravelMode example 2 (workflow)

This script shows how to find closest facilities based on a Trucking Time travel mode.

#Import modules
import os
import arcpy

#Define variables
workspace = "C:/data/SanDiego.gdb"
output_folder = "C:/data/output"
nds = os.path.join(workspace, "Transportation", "Streets_ND")
facilities = os.path.join(workspace, "WeightStations")
incidents = os.path.join(workspace, "RestAreaLocations")
analysis_layer_name = "ClosestFacility"

#Set environment variables
arcpy.env.overwriteOutput = True

#Check out the network analyst extension
arcpy.CheckOutExtension("network")

#Create a new closest facility analysis layer
make_layer_result = arcpy.na.MakeClosestFacilityLayer(nds, analysis_layer_name,
                                                      "TravelTime")
analysis_layer = make_layer_result.getOutput(0)

#Add facilities and incidents to the analysis layer using default field mappings         
sub_layer_names = arcpy.na.GetNAClassNames(analysis_layer)
facility_layer_name = sub_layer_names["Facilities"]
incident_layer_name = sub_layer_names["Incidents"]
arcpy.na.AddLocations(analysis_layer, facility_layer_name, facilities, "#", "#")
arcpy.na.AddLocations(analysis_layer, incident_layer_name, incidents, "#", "#")

#Get the Trucking Time travel mode from the network dataset
travel_modes = arcpy.na.GetTravelModes(nds)
trucking_mode = travel_modes["Trucking Time"]

#Apply the travel mode to the analysis layer
solver_properties = arcpy.na.GetSolverProperties(analysis_layer)
solver_properties.applyTravelMode(trucking_mode)

#Solve the analysis layer and save the result as a layer file          
arcpy.na.Solve(analysis_layer)

output_layer = os.path.join(output_folder, analysis_layer_name + ".lyr")
arcpy.management.SaveToLayerFile(analysis_layer, output_layer, "RELATIVE")

arcpy.AddMessage("Completed")