Summary
Makes a service area network analysis layer and sets its analysis properties. A service area analysis layer is useful in determining the area of accessibility within a given cutoff cost from a facility location.
Usage
After creating the analysis layer with this tool, you can add network analysis objects to it using the Add Locations tool, solve the analysis using the Solve tool, and save the results on disk using the Save To Layer File tool.
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When using this tool in geoprocessing models, if the model is run as a tool, the output network analysis layer must be made a model parameter; otherwise, the output layer is not added to the contents of the map.
Syntax
arcpy.na.MakeServiceAreaLayer(in_network_dataset, out_network_analysis_layer, impedance_attribute, {travel_from_to}, {default_break_values}, {polygon_type}, {merge}, {nesting_type}, {line_type}, {overlap}, {split}, {excluded_source_name}, {accumulate_attribute_name}, {UTurn_policy}, {restriction_attribute_name}, {polygon_trim}, {poly_trim_value}, {lines_source_fields}, {hierarchy}, {time_of_day})| Parameter | Explanation | Data Type |
in_network_dataset | The network dataset on which the service area analysis will be performed. | Network Dataset Layer |
out_network_analysis_layer | Name of the service area network analysis layer to create. | String |
impedance_attribute | The cost attribute to be used as impedance in the analysis. | String |
travel_from_to (Optional) | Specifies the direction of travel to or from the facilities.
Using this option can result in different service areas on a network with one-way restrictions and having different impedances based on direction of travel. The service area for a pizza delivery store, for example, should be created away from the facility, whereas the service area of a hospital should be created toward the facility. | String |
default_break_values (Optional) | Default impedance values indicating the extent of the service area to be calculated. The default can be overridden by specifying the break value on the facilities. 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 "2 3 5" as the value for the Default break values parameter (the numbers 2, 3, and 5 should be separated by a space). | String |
polygon_type (Optional) | Specifies the type of polygons to be generated.
If your data is of an urban area with a gridlike network, the difference between generalized and detailed polygons would be minimal. However, for mountain and rural roads, the detailed polygons may present significantly more accurate results than generalized polygons. | String |
merge (Optional) | Specifies the options to merge polygons that share similar break values. This option is applicable only when generating polygons for multiple facilities.
| String |
nesting_type (Optional) | Specifies the option to create concentric service area polygons as disks or rings. This option is applicable only when multiple break values are specified for the facilities.
| String |
line_type (Optional) | Specifies the type of lines to be generated based on the service area analysis. Selecting the TRUE_LINES or TRUE_LINES_WITH_MEASURES option for large service areas will increase the amount of memory consumed by the analysis.
| String |
overlap (Optional) | Determines if overlapping lines are generated when the service area lines are computed.
| Boolean |
split (Optional) |
| Boolean |
excluded_source_name [excluded_source_name,...] (Optional) | Specifies 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. This is useful if you have some network sources that you don't want to be included in the polygon generation because they create less accurate polygons or are inconsequential for the service area analysis. For example, while creating a drive time service area in a multimodal network of streets and rails, you should choose to exclude the rail lines from polygon generation so as to correctly model where a vehicle could travel. Excluding a network source from service area polygons does not prevent those sources from being traversed. Excluding sources from service area polygons only influences the polygon shape of the service areas. If you want to prevent traversal of a given network source, you must create an appropriate restriction when defining your network dataset. | String |
accumulate_attribute_name [accumulate_attribute_name,...] (Optional) | A list of cost attributes to be accumulated during analysis. These accumulation attributes are purely for reference; the solver only uses the cost attribute specified by the Impedance Attribute parameter to calculate the route. For each cost attribute that is accumulated, a Total_[Impedance] property is added to the routes that are output by the solver. | String |
UTurn_policy (Optional) | The U-Turn policy at junctions. Allowing U-turns implies the solver can turn around at a junction and double back on the same street. Given that junctions represent street intersections and dead ends, different vehicles may be able to turn around at some junctions but not at others—it depends on whether the junction represents an intersection or dead end. To accommodate this, the U-turn policy parameter is implicitly specified by how many edges connect to the junction, which is known as junction valency. The acceptable values for this parameter are listed below; each is followed by a description of its meaning in terms of junction valency.
If you need a more precisely defined U-turn policy, consider adding a global turn delay evaluator to a network cost attribute, or adjusting its settings if one exists, and pay particular attention to the configuration of reverse turns. Also, look at setting the CurbApproach property of your network locations. | String |
restriction_attribute_name [restriction_attribute_name,...] (Optional) | A list of restriction attributes to apply during the analysis. | String |
polygon_trim (Optional) |
| Boolean |
poly_trim_value (Optional) | Specifies the distance within which the service area polygons are trimmed. The parameter includes a value and units for the distance. The default value is 100 meters. | Linear Unit |
lines_source_fields (Optional) |
| Boolean |
hierarchy (Optional) |
The parameter is not used if a hierarchy attribute is not defined on the network dataset used to perform the analysis. In such cases, use "#" as the parameter value. | Boolean |
time_of_day (Optional) | The time to depart from or arrive at the facilities of the service area layer. The interpretation of this value as a depart or arrive time depends on whether travel is away from or toward the facilities.
If you have chosen a traffic-based impedance attribute, the solution will be generated given dynamic traffic conditions at the time of day specified here. A date and time can be specified as 5/14/2012 10:30 AM. Instead of using a particular date, a day of the week can be specified using the following dates:
Repeatedly solving the same analysis, but using different Time of Day values, allows you to see how a facility's reach changes over time. For instance, the five-minute service area around a fire station may start out large in the early morning, diminish during the morning rush hour, grow in the late morning, and so on throughout the day. | Date |
Derived Output
| Name | Explanation | Data Type |
| output_layer | The newly created network analysis layer. | Network Analyst Layer |
Code sample
MakeServiceAreaLayer example 1 (Python window)
Execute the tool using only the required parameters.
network = "C:/Data/SanFrancisco.gdb/Transportation/Streets_ND"
arcpy.na.MakeServiceAreaLayer(network, "FireStationCoverage", "TravelTime")
MakeServiceAreaLayer example 2 (Python window)
Execute the tool using all parameters.
network = "C:/Data/Paris.gdb/Transportation/ParisMultimodal_ND"
arcpy.na.MakeServiceAreaLayer(network, "WarehouseCoverage", "DriveTime",
"TRAVEL_FROM", "5 10 15", "SIMPLE_POLYS",
"NO_OVERLAP", "RINGS", "TRUE_LINES",
"NON_OVERLAP", "NO_SPLIT",
["Metro_Lines", "Transfer_Stations",
"Transfer_Street_Station"],
["Meters", "DriveTime"], "ALLOW_DEAD_ENDS_ONLY",
["Oneway"], "NO_TRIM_POLYS", "",
"LINES_SOURCE_FIELDS")
MakeServiceAreaLayer example 3 (workflow)
The following stand-alone Python script demonstrates how the MakeServiceAreaLayer tool can be used to generate a 1-, 2-, and 3-minute service area around fire stations.
# Name: MakeServiceAreaLayer_Workflow.py
# Description: Generate 1-,2-,3- minute service area around fire stations and
# save the results to a layer file on disk. The service area
# polygons can be used to visualize the areas that do not have
# adequate coverage from the fire stations
# Requirements: Network Analyst Extension
#Import system modules
import arcpy
from arcpy import env
try:
#Check out the Network Analyst extension license
arcpy.CheckOutExtension("Network")
#Set environment settings
env.workspace = "C:/data/SanFrancisco.gdb"
env.overwriteOutput = True
#Set local variables
inNetworkDataset = "Transportation/Streets_ND"
outNALayerName = "FireStationCoverage"
impedanceAttribute = "TravelTime"
inFacilities = "Analysis/FireStations"
outLayerFile = "C:/data/output" + "/" + outNALayerName + ".lyr"
#Create a new service area layer. We wish to generate the service area
#polygons as rings, so that we can easily visualize the coverage for any
#given location. We also want overlapping polygons as we can determine the
#number of fire stations that cover a given location. We use hierarchy to
#speed up the time taken to create the polygons. We will specify these
#options while creating the new service area layer.
outNALayer = arcpy.na.MakeServiceAreaLayer(inNetworkDataset, outNALayerName,
impedanceAttribute, "TRAVEL_FROM", "1 2 3",
"SIMPLE_POLYS", "NO_MERGE", "RINGS",
hierarchy = "USE_HIERARCHY")
#Get the layer object from the result object. The service layer can now be
#referenced using the layer object.
outNALayer = outNALayer.getOutput(0)
#Get the names of all the sublayers within the service area layer.
subLayerNames = arcpy.na.GetNAClassNames(outNALayer)
#Stores the layer names that we will use later
facilitiesLayerName = subLayerNames["Facilities"]
#Load the fire stations as facilities using default field mappings and
#default search tolerance
arcpy.na.AddLocations(outNALayer, facilitiesLayerName, inFacilities, "", "")
#Solve the service area layer
arcpy.na.Solve(outNALayer)
#Save the solved service area layer as a layer file on disk with relative
#paths
arcpy.management.SaveToLayerFile(outNALayer,outLayerFile,"RELATIVE")
print "Script completed successfully"
except Exception as e:
# If an error occurred, print line number and error message
import traceback, sys
tb = sys.exc_info()[2]
print "An error occurred on line %i" % tb.tb_lineno
print str(e)
MakeServiceAreaLayer example 4 (workflow)
This example shows how to create service areas around facilities for multiple times of the day, as well as how to port fields from the input features to the output features and append output polygons to an existing feature class.
# Name: MakeServiceAreaLayer_Workflow2.py
# Description: Generate 3-minute service areas around fire stations at several
# times of day to compare coverage differences due to varying
# traffic conditions. Save the results to a feature class on disk.
# Requirements: Network Analyst Extension
import datetime
#Import system modules
import arcpy
from arcpy import env
try:
#Check out the Network Analyst extension license
arcpy.CheckOutExtension("Network")
#Set environment settings
env.workspace = "C:/Data/SanFrancisco.gdb"
env.overwriteOutput = True
#Set local variables
inNetworkDataset = "Transportation/Streets_ND"
outNALayerName = "FireStationCoverage"
outSAFC = "Analysis/outSAPolys"
impedanceAttribute = "TravelTime"
inFacilities = "Analysis/FireStations"
timelist = [datetime.datetime(2013, 8, 23, 7, 0, 0),
datetime.datetime(2013, 8, 23, 12, 30, 0),
datetime.datetime(2013, 8, 23, 17, 30, 0),
datetime.datetime(2013, 8, 23, 21, 0, 0)]
#Create a new service area layer.
outSAResultObject = arcpy.na.MakeServiceAreaLayer(inNetworkDataset, outNALayerName,
impedanceAttribute, "TRAVEL_FROM", "3",
"DETAILED_POLYS", "NO_MERGE",
hierarchy = "NO_HIERARCHY")
#Get the layer object from the result object. The service area layer can
#now be referenced using the layer object.
outNALayer = outSAResultObject.getOutput(0)
#Get the names of all the sublayers within the service area layer.
subLayerNames = arcpy.na.GetNAClassNames(outNALayer)
#Store the layer names that we will use later
facilitiesLayerName = subLayerNames["Facilities"]
polygonsLayerName = subLayerNames["SAPolygons"]
#The input data has a field for FireStationID that we want to transfer to
#our analysis layer. Add the field, and then use field mapping to transfer
#the values.
arcpy.na.AddFieldToAnalysisLayer(outNALayer, facilitiesLayerName,
"FireStationID", "TEXT")
fieldMappings = arcpy.na.NAClassFieldMappings(outNALayer,
facilitiesLayerName)
fieldMappings["FireStationID"].mappedFieldName = "FireStationID"
#Load the fire stations as facilities.
arcpy.na.AddLocations(outNALayer, facilitiesLayerName, inFacilities,
fieldMappings, "",
exclude_restricted_elements = "EXCLUDE")
#Get sublayers we will want to work with later
FacilitiesSubLayer = arcpy.mapping.ListLayers(outNALayer,
facilitiesLayerName)[0]
PolygonsSubLayer = arcpy.mapping.ListLayers(outNALayer,
polygonsLayerName)[0]
# Add fields to the output Polygons sublayer. We will fill the values later.
arcpy.na.AddFieldToAnalysisLayer(outNALayer, polygonsLayerName,
"FireStationID", "TEXT")
arcpy.na.AddFieldToAnalysisLayer(outNALayer, polygonsLayerName,
"TimeOfDay", "TEXT")
#Get the Service Area Layer's solver properties. This will allow us to
#set individual properties later without re-creating the layer.
SA_SolverProperties = arcpy.na.GetSolverProperties(outNALayer)
#Solve the Service Area for each time of day in our time list
for t in timelist:
print "Now solving for time of day: " + str(t)
#Use the solver properties to set the time of day for the solve
SA_SolverProperties.timeOfDay = t
#Solve the service area layer
arcpy.na.Solve(outNALayer)
#Transfer the FireStationID field from the input Facilities to the
#output Polygons
arcpy.management.AddJoin(PolygonsSubLayer, "FacilityID",
FacilitiesSubLayer, "ObjectID")
arcpy.management.CalculateField(PolygonsSubLayer, "FireStationID",
"!Facilities.FireStationID!", "PYTHON")
arcpy.management.RemoveJoin(PolygonsSubLayer)
#Populate the TimeOfDay field
expression = '"' + str(t) + '"'
arcpy.management.CalculateField(PolygonsSubLayer, "TimeOfDay",
expression, "PYTHON")
#Append the polygons to the output feature class. If this was the first
#solve, create the feature class.
if not arcpy.Exists(outSAFC):
arcpy.management.CopyFeatures(PolygonsSubLayer, outSAFC)
else:
arcpy.management.Append(PolygonsSubLayer, outSAFC)
print "Script completed successfully"
except Exception as e:
# If an error occurred, print line number and error message
import traceback, sys
tb = sys.exc_info()[2]
print "An error occurred on line %i" % tb.tb_lineno
print str(e)
Environments
Licensing information
- Basic: Yes
- Standard: Yes
- Advanced: Yes