Empty output is returned by the Make Route Event Layer tool

Description

The Make Route Event Layer tool creates a temporary feature layer using routes and a route events layer. In some instances, running the tool returns an empty output layer, despite the input layer being M-enabled.

Cause

The Make Route Event Layer tool produces an empty output when a feature class is used as an input, instead of a route feature class. A common misconception is that a route feature class is just an M-enabled feature class. However, M-enabled feature classes only have the capability of storing M-values and do not necessarily contain M-values; they are not necessarily route feature classes.

Solution or Workaround

The M-values of each feature can be checked by using the Add Geometry Attributes tool and adding a field with M-values. The field must be populated with non-null values. If the M-values of the geometry are not desired for use on the route, the values can be changed in the fields before using the fields as the source of M-values in the Create Routes tool.

Once the M-values are set up (either in the geometry or in fields), use the Create Routes tool from the Linear Referencing toolbox to generate a route layer containing the M-values. Using the output layer of this tool as the input in the Make Route Event Layer tool yields the desired outcome.