The Ex3.mxd map contains several layers in a data frame called Pitt County. They are:
calibration_points: The points used in the previous segment to recalibrate the route measures.
base_roads: All of the roads in Pitt County
city boundaries: The boundaries of the cities in Pitt County
county boundary: The Pitt County boundary
When it is first opened, the map displays the city boundaries and county boundary layers. Their check boxes are checked in the table of contents. The calibration_points layer is checked, but scale dependent rendering was set for this layer. It is only visible when you zoom in closer that 1:25,000 scale.

The base_roads layer contains all of the roads in Pitt County. This includes roads not maintained by the highway authority. The roads maintained by the highway authority were written to the routes feature class.

To add route data to a map, click the Add Data button, navigate to the route feature class, select it (or select more than one feature class by pressing the Ctrl key while you click the feature classes), and click Add.

The colors and symbols with which the routes are displayed when first added to ArcMap may make it difficult to see where the route features are located. They may not contrast with the base_roads, over which they are drawn. It is easy to change the colors and symbols used to display features in ArcMap.

To change the symbol for a layer, click the symbol in the table of contents to open the Symbol Selector dialog box. You can also open the Symbol Selector dialog box by right-clicking the layer in the table of contents, clicking Properties, and clicking the Symbology tab. To simply change the color of a symbol, right-click the symbol in the table of contents to display the color palette, click any color or More Colors.

Layers of route data have some additional layer properties in ArcMap. One of these properties is the Route Identifier field. The contents of this field uniquely identify each route for the linear referencing tools in ArcMap.

Setting the Route Identifier field is not required. Doing so, however, reduces the number of steps required to use many of the ArcMap Linear Referencing dialog boxes, tools, and wizards.

To set the Route Identifier field, right-click the route layer in the table of contents and click Properties. Click the Routes tab, then click the Route Identifier dropdown arrow and click the field that contains the route identifier codes. In this example it is called ROUTE1.