Network analysis with parameterized attributes
You can perform a network analysis that uses a parameterized attribute while computing the solution.
The first step to performing a network analysis using a parameterized attribute is to have a network dataset with a parameterized attribute.
Learn more about using parameters with network attributes
What are parameterized attributes?
A parameterized attribute is a type of attribute that includes in its evaluation a parameter that you can change at solve time.
The value of a parameter can be altered to make the parameterized attribute change the way it functions. For example, you can enter a scale factor on a parameterized drive-time attribute to increase travel times for a given solve operation. You can specify the height of a vehicle on a parameterized restriction attribute so that routes don't traverse edges that have a maximum height value that is less than the vehicle's height.
The Restriction Usage parameter
By default, all restriction attributes are assigned a parameter: Restriction Usage. You choose a value for this parameter to prefer, avoid, or entirely prohibit network elements that use the restriction; furthermore, you specify the degree to which elements are avoided or preferred.
Most often, this attribute is set to Prohibit. Certainly, you would choose Prohibit for restrictions based on physical limits, like height limits. However, you can choose to merely avoid or even prefer network elements by choosing other values; for example, you might avoid toll roads or prefer designated truck routes when routing trucks.
Performing a network analysis in ArcMap using a parameterized attribute
You can apply the following workflow to use parameterized attributes in any network analysis. First, ensure that you have an analysis layer and all required network analysis objects before carrying out these steps.
On the Table Of Contents window, double-click the network analysis layer to view its properties.
Click the Analysis Settings tab.
Set the parameterized attributes to be used in the analysis. To use a parameterized cost attribute, choose it for the Impedance setting. To use parameterized restriction attributes, check them in the Restrictions section.
For example, you could change Impedance to read a parameterized scaled cost attribute and check Height, Hazmats Prohibited, and Hazmats Preferred restrictions.
Click the Attribute Parameters tab.
If you need to adjust any of the parameter values for the attributes, click in the Values column for the row with the right attribute-parameter combination and update the parameter value.
For example, the following changes could be made to an analysis, assuming the network dataset has the appropriate attributes and parameters:
Set the Drive Time Factor parameter of the DriveTime_Scaled cost attribute to 1.5 to increase travel times by 50 percent to account for icy roads.
Set the Vehicle Height parameter of the Height attribute to 13.5 feet to represent the height of the vehicle for which you are currently solving an analysis.
Set the Restriction Usage parameter of the same Height attribute to Prohibited since you would never want your vehicle to try to drive under a bridge with a minimum clearance that is lower than the height of your vehicle.
Set the Restriction Usage parameter of the Hazmats Prohibited attribute to Prohibited to never allow the vehicle for which you're solving to go on roads that are posted as prohibited to hazmat vehicles.
If detouring around roads that are off limits to hazmat vehicles isn't an option—for instance, a stop the truck must visit is on such a road—you can relax the constraint by changing the Restriction Usage parameter value from Prohibit to Avoid: High. This causes the solver to try to stay off the restricted roads; it travels on them only if detouring around the roads is too costly or if a restricted road must be traversed to reach a stop.
Set the Restriction Usage parameter of the Hazmats Preferred attribute to Prefer: Low, Prefer: Medium, or Prefer: High. The choice of low, medium, or high depends on whether it is slightly, somewhat, or very important that your truck stays on designated hazmat roads as much as possible.
Click OK to save these settings.
On the Network Analyst toolbar, click the Solve button
to generate results that use these parameterized attributes.