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ServiceAreaSolverProperties

Summary

Provides access to analysis properties from a service area network analysis layer. The GetSolverProperties function is used to obtain a ServiceAreaSolverProperties object from a service area network analysis layer.

Discussion

The ServiceAreaSolverProperties object provides read and write access to all the analysis properties of a service area network analysis layer. The object can be used to modify the desired analysis properties of the service area layer, and the corresponding layer can be resolved to determine the appropriate results. A new service area layer can be created using the Make Service Area Analysis Layer geoprocessing tool. Obtaining the ServiceAreaSolverProperties object from a new service area 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 of the ServiceAreaSolverProperties 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

PropertyExplanationData 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.

Do not attempt to modify the attributeParameters property in place; this coding method will not work.

solverProps.attributeParameters[('HeightRestriction', 'RestrictionUsage')] = "PROHIBITED"

Modify the attributeParameters property using a new dictionary object.

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
defaultBreaks
(Read and Write)

Provides the ability to get or set the impedance values, indicating the extent of the service area to be calculated. Multiple polygon breaks can be set to create concentric service areas. For instance, to find 2-, 3-, and 5-minute service areas for the same facility, specify the value as [2, 3, 5].

Double
excludeSources
(Read and Write)

Provides the ability to get or set the list of network sources to be excluded when generating the polygons. The geometry of traversed elements from the excluded sources will be omitted from all polygons. An empty list, [], indicates that no network sources are excluded.

String
impedance
(Read and Write)

Provides the ability to get or set the network cost attribute used as impedance. This cost attribute is accumulated while determining the service area.

String
includeNetworkSourceFields
(Read and Write)

Controls whether additional fields from the underlying source features traversed during the analysis are added to the service area lines. The following is a list of possible values:

  • LINES_SOURCE_FIELDS Add the SourceID, SourceOID, FromPosition, and ToPosition fields to the service area lines to hold information about the underlying source features traversed during the analysis. This can be useful to join the results of the service area lines to the original source data. A value of True can also be used to specify this option.
  • NO_LINES_SOURCE_FIELDSDo not add the source fields (SourceID, SourceOID, FromPosition, and ToPosition) to the service area lines. A value of False can also be used to specify this option.
String
lineOverlap
(Read and Write)

Controls whether overlapping lines are generated when the service area lines are computed. The following is a list of possible values:

  • OVERLAP Include a separate line feature for each facility when the facilities have service area lines that are coincident. A value of True can also be used to specify this option.
  • NON_OVERLAP Include each service area line once and associate it with its closest (least impedance) facility. A value of False can also be used to specify this option.
String
lineType
(Read and Write)

Provides the ability to get or set the type of service area lines to be generated from the analysis. The following is a list of possible values:

  • NO_LINESDo not generate lines.
  • TRUE_LINESLines are generated without measures.
  • TRUE_LINES_WITH_MEASURESLines are generated with measures. The measure values are generated based on the impedance value on each end of the edge with the intermediate vertices interpolated. Do not use this option if faster performance is desired.
String
polygonMerge
(Read and Write)

Controls whether polygons that share similar break values are merged. This option is applicable only when generating polygons for multiple facilities. The following is a list of possible values:

  • NO_MERGECreate individual polygons for each facility. The polygons can overlap each other.
  • NO_OVERLAPCreate individual polygons that are closest for each facility. The polygons do not overlap each other.
  • MERGE Join the polygons of multiple facilities that have the same break value.
String
polygonNesting
(Read and Write)

Controls whether concentric service area polygons are created as disks or rings. This option is applicable only when multiple break values are specified for the facilities. The following is a list of possible values:

  • RINGSDo not include the area of the smaller breaks. This creates polygons going between consecutive breaks. Use this option if you want to find the area from one break to another. A value of True can also be used to specify this option.
  • DISKS Create the polygons going from the facility to the break. For instance, If you create 5- and 10-minute service areas, then the 10-minute service area polygon will include the area under the 5-minute service area polygon. Use this option if you want to find the entire area from the facility to the break for each break. A value of False can also be used to specify this option.
String
polygonType
(Read and Write)

Provides the ability to get or set the type of polygons to be generated. The following is a list of possible values:

  • SIMPLE_POLYSCreate generalized polygons that are generated quickly and are fairly accurate, except on the fringes.
  • DETAILED_POLYSCreate detailed polygons that accurately model the service area lines and may contain islands of unreached areas. This option is a lot slower than generating generalized polygons.
  • NO_POLYSTurns off polygon generation for the case in which only service area lines are desired.
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 analysis layer used to obtain the solver properties object. The property always returns the string value Service Area Solver when accessed from a ServiceAreaSolverProperties object.

String
splitLinesAtBreaks
(Read and Write)

Controls whether service area lines are split when they cross a break value. The following is a list of possible values:

  • SPLITSplit every line between two breaks into two lines, each lying within its break. This is useful if you want to symbolize the service area lines by break; otherwise, use the NO_SPLIT option for optimal performance.
  • NO_SPLITThe lines are not split at the boundaries of the breaks.
String
timeOfDay
(Read and Write)

Provides the ability to get or set the time to depart from or arrive at the facilities. The interpretation of this value depends on whether travel is toward or away from the facilities. It represents the departure time if the travelDirection property is set to TRAVEL_FROM and represents the arrival time if the travelDirection property is set to TRAVEL_TO. 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 departure from facilities should occur at 8:00 a.m. on Friday, specify the value as datetime.datetime(1900, 1, 5, 8,0,0).

The timeZoneUsage parameter specifies whether the date and time refer to UTC or the time zone in which the facilities are located.

DateTime
timeZoneUsage
(Read and Write)

Specifies the time zone or zones of the timeOfDay parameter.

  • GEO_LOCALThe timeOfDay parameter refers to the time zone or zones in which the facilities are located. Therefore, the start or end times of the service areas are staggered by time zone.Setting timeOfDay to 9:00 a.m., choosing GEO_LOCAL, then solving causes service areas to be generated for 9:00 a.m. Eastern Time for any facilities in the Eastern Time Zone, 9:00 a.m. Central Time for facilities in the Central Time Zone, 9:00 a.m. Mountain Time for facilities in the Mountain Time Zone, and so on, for facilities in different time zones. The time is always 9:00 a.m. local time, but staggered in real time.If stores in a chain that span the U.S. open at 9:00 a.m. local time, this parameter value could be chosen to find market territories at opening time for all stores in one solve. First, the stores in the Eastern Time Zone open and a polygon is generated, stores open an hour later in Central Time, and so on.
  • UTCThe timeOfDay parameter refers to Coordinated Universal Time (UTC). Therefore, all facilities are reached or departed from simultaneously, regardless of the time zone or zones they are in.Setting timeOfDay to 2:00 p.m., choosing UTC, then solving causes service areas to be generated for 9:00 a.m. Eastern Standard Time for any facilities in the Eastern Time Zone, 8:00 a.m. Central Standard Time for facilities in the Central Time Zone, 7:00 a.m. Mountain Standard Time for facilities in the Mountain Time Zone, and so on, for facilities in different time zones.
    Note:

    The scenario above assumes standard time. During daylight saving time, the Eastern, Central, and Mountain times would each be one hour ahead (that is, 10:00, 9:00, and 8:00 a.m., respectively).

    One of the cases in which the UTC option is useful is to visualize emergency-response coverage for a jurisdiction that is split into two time zones. The emergency vehicles are loaded as facilities. timeOfDay is set to now in UTC. (You need to determine the current time and date in UTC to correctly use this option.) Other properties are set, and the analysis is solved. Even though a time-zone boundary divides the vehicles, the results show areas that can be reached given current traffic conditions. This same process can be used for other times as well, not just for now.

Irrespective of the timeZoneUsage setting, all facilities must be in the same time zone when timeOfDay has a nonnull value and polygonMerge is set to create merged or nonoverlapping polygons.

String
travelDirection
(Read and Write)

Controls the direction in which the impedance is accumulated during service area analysis. The following is a list of possible values:

  • TRAVEL_FROMThe service area is created in the direction away from the facilities.
  • TRAVEL_TOThe service area is created in the direction toward the facilities.
String
travelMode
(Read Only)

Accesses the travel mode set on a network analysis layer as an arcpy.na.TravelMode object.

Object
trimDistance
(Read and Write)

Provides the ability to get or set the distance within which the service area polygons are trimmed. The property value includes a numeric value and a unit for the distance separated by a space; for example, to specify a trim distance of 100 Meters, use "100 Meters".

String
trimPolygons
(Read and Write)

Controls whether the service area polygons are trimmed. The following is a list of possible values:

  • TRIM_POLYSTrim the polygons containing the edges at the periphery of the service area to be within the specified distance of these outer edges. This is useful if the network is very sparse and you don't want the service area to cover large areas where there are no features. A value of True can also be used to specify this option.
  • NO_TRIM_POLYSDo not trim polygons. A value of False can also be used to specify this option.
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_HIERARCHYDo 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_UTURNSU-turns are permitted at junctions with any number of connected edges.
  • NO_UTURNSU-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_ONLYU-turns are prohibited at all junctions, except those that have only one adjacent edge (a dead end).
  • ALLOW_DEAD_ENDS_AND_INTERSECTIONS_ONLYU-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

MethodExplanation
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)
ParameterExplanationData 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

ServiceAreaSolverProperties example 1 (Python window)

The script shows how to update a service area network analysis layer to use hierarchy and set 5, 10, and 15 minutes as the break values. It assumes that a service area layer called Store Trade Areas has been created in a new map document based on the tutorial network dataset for the San Francisco region.

#Get the service area layer object from a layer named "Store Trade Areas" in
#the map
doc = arcpy.mp.ArcGISProject('current')
map_obj = doc.listMaps()[0]
sa_layer = map_obj.listLayers("Store Trade Areas")[0]

#Get the solver properties object from the service area layer
solver_props = arcpy.na.GetSolverProperties(sa_layer)

#Update the properties for the service area layer using the solver properties
#object
solver_props.defaultBreaks = [5, 10, 15]
solver_props.useHierarchy = "USE_HIERARCHY"
ApplyTravelMode example 2 (Python window)

This script shows how to apply the TruckingTime travel mode to an existing layer.

#Get the service area layer object from a layer named "Service Area" in the map
doc = arcpy.mp.ArcGISProject('current')
map_obj = doc.listMaps()[0]
sa_layer = map_obj.listLayers('Service Area')[0]

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

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

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