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Problem: Network Analyst: Routes travel the wrong way on one-way streets

Description

When performing network analysis with the Network Analyst extension, the resulting route travels the wrong way on streets known to be one-way.

Cause

Possible causes to this problem:
- The network analysis layer is not configured to use a one-way restriction attribute.
- There is not a one-way restriction attribute defined in the network dataset.
- The evaluator defined for the one-way restriction's attribute is incorrect.

Solution or Workaround

Follow these steps to resolve the problem.

  • The most common solution is to change the properties of the network analysis layer to use the one-way restriction attribute. To do so within ArcMap, open the properties for the network analysis layer, click on the 'Analysis Settings' tab, and check on the one-way attribute in the restrictions list.
  • If there is not a one-way attribute in the analysis layer's restrictions list, the underlying network dataset does not have a one-way restriction attribute. Create this attribute by doing the following:

    Within ArcCatalog, navigate to the network dataset and open its properties. Click on the Settings tab. Create a new attribute named something like 'OneWay' of type 'Restriction'. Click on 'Evaluators' and set up the appropriate evaluator for the one-way attribute based on the underlying data. This will most likely be a field evaluator.

    Make sure to rebuild the network dataset prior to performing analysis after making this change.
  • If there is already a one-way attribute defined for the network dataset, it is specified as restricted in the analysis layer and it is still traveling the wrong way, then the evaluator defined incorrectly. Modify the evaluator to have the appropriate expression based on the underlying data and rebuild the network dataset.

    It is possible to verify that the restriction attributes are set correctly by using the network identify tool in ArcMap.