RouteSolverProperties

Summary

Provides access to analysis properties from a route network analysis layer. The GetSolverProperties function is used to obtain a RouteSolverProperties object from a route network analysis layer.

Discussion

The RouteSolverProperties object provides read and write access to all the analysis properties of a route network analysis layer. The object can be used to modify the desired analysis properties of the route layer, and the corresponding layer can be re-solved to determine the appropriate results. A new route layer can be created using the Make Route Layer geoprocessing tool. Obtaining the RouteSolverProperties object from a new route 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 RouteSolverProperties 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
findBestSequence (Read and Write)	Controls whether the stops are reordered to find optimal routes. The following is a list of possible values: FIND_BEST_ORDER —The stops will be reordered to find the optimal route. This option changes the route analysis from a shortest-path problem to a traveling salesperson problem (TSP). A value of True can also be used to specify this option. USE_INPUT_ORDER —The stops will be visited in the input order. A value of False can also be used to specify this option.	String
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 best route.	String
orderingType (Read and Write)	Controls the ordering of stops when findBestSequence property is set to FIND_BEST_ORDER. The following is a list of possible values: PRESERVE_BOTH —Preserves the first and last stops by input order as the first and last stops in the route. PRESERVE_FIRST —Preserves the first stop by input order as the first stop in the route, but the last stop is free to be reordered. PRESERVE_LAST —Preserves the last stop by input order as the last stop in the route, but the first stop is free to be reordered. PRESERVE_NONE —Frees both the first and last stop to be reordered.	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 the stops. 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 analysis layer used to obtain the solver properties object. The property always returns the string value Route Solver when accessed from a RouteSolverProperties object.	String
timeOfDay (Read and Write)	Provides the ability to get or set the start date and time for the route. Route start time is mostly used to find routes based on the impedance attribute that varies with the time of the day. For example, a start time of 9 a.m. could be used to find a route that considers the rush-hour traffic. 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 at 5:00 p.m. on Tuesday, specify the value as datetime.datetime(1900, 1, 2, 17,0,0). The timeZoneUsage parameter specifies whether the date and time refer to UTC or the time zone in which the first stop is located.	DateTime
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 first stop is located. UTC —The timeOfDay parameter refers to Coordinated Universal Time (UTC). Choose this option if you want to solve the analysis for a specific time, such as now, but aren't certain in which time zone the facilities or demand points will be located. When solving a route analysis that spans across multiple time zones and setting a start time, the orderingType cannot be set to PRESERVE_NONE. A starting location and time zone must be fixed.	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
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
useTimeWindows (Read and Write)	Controls if time windows will be used at the stops. The following is a list of possible values: USE_TIMEWINDOWS —The route will consider time windows on the stops. If a stop is arrived at before its time window, there will be wait time until the time window starts. If a stop is arrived at after its time window, there will be a time-window violation. Total time-window violation is balanced against minimum impedance when computing the route. This option is applicable only when the network cost attribute specified as the value for impedance property is in time units. A value of True can also be used to specify this option. NO_TIMEWINDOWS —The route will ignore time windows on the stops. A value of False can also be used to specify this option.	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

RouteSolverProperties example 1 (Python window)

The script shows how to update the impedance property to the TravelTime cost attribute, specify Minutes and Meters cost attributes as accumulative attributes, and use the current time as the route start time. It assumes that a route network analysis layer called Route has been created in a new map document based on the tutorial network dataset for San Francisco region.

#Get the route layer object from a layer named "Route" in the table of contents
routeLayer = arcpy.mapping.Layer("Route")

#Get the route solver properties object from the route layer
solverProps = arcpy.na.GetSolverProperties(routeLayer)

#Update the properties for the route layer using the route solver properties object
solverProps.impedance = "TravelTime"
solverProps.accumulators = ["Meters", "Minutes"]
#Only set the time component from the current date time as time of day
solverProps.timeOfDay = datetime.datetime.now().time()

RouteSolverProperties example 2 (workflow)

The script shows how to find a shortest (distance) and fastest (travel time) route between a set of stops and save each route as a feature class in a geodatabase. It illustrates how to create only one instance of a route layer and modify the impedance property using the RouteSolverProperties object to achieve the desired results.

import arcpy

#Set up the environment
arcpy.env.overwriteOutput = True
arcpy.CheckOutExtension("network")

#Set up variables
networkDataset = "C:/Data/SanFrancisco.gdb/Transportation/Streets_ND"
stops = "C:/Data/SanFrancisco.gdb/Analysis/Stores"
fastestRoute = "C:/Data/SanFrancisco.gdb/FastestRoute"
shortestRoute = "C:/Data/SanFrancisco.gdb/ShortestRoute"

#Make a new route layer using travel time as impedance to determine fastest route
routeLayer = arcpy.na.MakeRouteLayer(networkDataset, "StoresRoute",
                                     "TravelTime").getOutput(0)

#Get the network analysis class names from the route layer
naClasses = arcpy.na.GetNAClassNames(routeLayer)

#Get the routes sublayer from the route layer
routesSublayer = arcpy.mapping.ListLayers(routeLayer, naClasses["Routes"])[0]

#Load stops
arcpy.na.AddLocations(routeLayer, naClasses["Stops"], stops)

#Solve the route layer
arcpy.na.Solve(routeLayer)

#Copy the route as a feature class
arcpy.management.CopyFeatures(routesSublayer, fastestRoute)

#Get the RouteSolverProperties object from the route layer to modify the
#impedance property of the route layer.
solverProps = arcpy.na.GetSolverProperties(routeLayer)

#Set the impedance property to "Meters" to determine the shortest route.
solverProps.impedance = "Meters"

#Resolve the route layer
arcpy.na.Solve(routeLayer)

#Copy the route as a feature class
arcpy.management.CopyFeatures(routesSublayer, shortestRoute)

arcpy.AddMessage("Completed")

ApplyTravelMode example 3 (workflow)

This script shows how to find a route 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")
stops = os.path.join(workspace, "TruckStops")
analysis_layer_name = "TruckRoute"

#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.MakeRouteLayer(nds, analysis_layer_name, "TravelTime")
analysis_layer = make_layer_result.getOutput(0)

#Add stops to the analysis layer using default field mappings         
sub_layer_names = arcpy.na.GetNAClassNames(analysis_layer)
stops_layer_name = sub_layer_names["Stops"]
arcpy.na.AddLocations(analysis_layer, stops_layer_name, stops, "#", "#")

#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")