During the life-span of a highway, the roadway may change its shape and length over time. Portions of the roadway are removed while others are added. Major changes, such as widening a road, building a new subdivision, or creating an interchange, may require a significant change in the shape of the road's geometry and length. Roads and Highways uses centerlines to perform such realignments. The centerline features used to realign routes can be existing features in the centerline feature class, be digitized into the centerline feature class (using aerial photography or other basemaps for guidance), copied and pasted from other feature classes, or imported from CAD files or other ArcGIS-supported data sources. In addition to realigning a portion of or the entire route, the Realign Route tool can update calibration points and apply end-user-configured event behaviors located along the realigned route. For more information, see Event behaviors.
- Start ArcMap and set up your editing environment for using Roads and Highways.
- Start an edit session and use the ArcMap navigation tools to zoom to the portion of the route you want to realign.
For more information on how to start an edit session, see About edit sessions.
- Click the Networks drop-down arrow on the Roads And Highways Editing toolbar to choose the LRS Network layer you want to edit.
- Click the Choose Centerlines button
on the Roads And Highways Editing toolbar and click an existing centerline in the map at the location of the route segment to be realigned.You can use multiple centerlines to realign a route. For more information, see Choosing centerlines for editing activities.
The selected centerline is highlighted in blue, and the arrow shows the direction of digitization. The centerline provides the location and geometry of the realigned portion of the route.
Press the Shift key and click the individual centerlines to select or deselect them. The features are labeled on the map based on the order of selection.
- Click the Realign Route button
on the Roads And Highways Editing toolbar.The Realign Route dialog box appears.
Realign Route dialog box 
- Type a date in the Effective Date field.
You can also click the calendar drop-down arrow and select the alignment date from the calendar.
The time is automatically set to 12:00:00 AM. You can edit this value.
- Type a Route ID in the Route ID text box. You can also click the Select Location From Map button
to choose the route to realign. - The From Measure value is automatically populated. It is calculated by the geometric length of the centerline minus (-) the To Measure. This value forms the From Measure of the realigned portion of the route.
- You can also type the From Measure value.
- You can click the Select From Measure tool
and click the map at the location of the From Measure value. If you do not know the From Measure value, you can allow Roads and Highways to suggest one. To do so, click the Calculate Measures button 
.
- The To Measure value is automatically populated. It is calculated by the geometric length of the centerline plus (+) the To Measure. This value forms the To Measure of the realigned portion of the route.
- You can also type the To Measure value.
- You can click the Select To Measure tool and click the map at the location of the To Measure value. If you do not know the To Measure value, you can allow Roads and Highways to suggest the To Measure. To do so, click the Calculate Measures button .
- Determine whether you want to recalibrate your route downstream and check or uncheck the Recalibrate route downstream check box as appropriate.
- When you choose to recalibrate downstream, the route has its downstream measures updated to reflect the new measures provided at the location of the realignment. Roads and Highways places a calibration point at the intersection of the new and original route segments on the route and adjusts measures along the route at the first calibration point encountered prior to the realignment.
- If you choose not to calibrate downstream, the To Measure value of the original route remains the same and is not updated downstream to reflect any new measure values. It is important to note that not recalibrating downstream could result in routes that are not monotonic, meaning that the measures on the routes are not strictly increasing or strictly decreasing.
Realign Route dialog box 
Realigned route without downstream calibration - Provide the split From Measure value.
- You can type a From Measure value.
- You can also click the Select From Measure tool and click the map at the location of the From measure value. The split From measure value is not required to be the same measure location where the realignment centerline touches the route, but in most scenarios it will be.
This value denotes the starting point of the realigned section on the original route.
- Provide the split To Measure value.
- You can type a To Measure value.
- You can also click the Select To Measure tool and click the map at the location of the To measure value. The split To measure value is not required to be the same measure location where the realignment centerline touches the route, but in most scenarios it will be.
This value denotes the ending point of the realigned section on the original route.
- If you want to apply measure behaviors to the route or portion of the route you are realigning, leave the Do not apply event measure behaviors box unchecked. If you do not want to apply measure behaviors along the route, check the check box.
- Click OK.
If the edit activity results in introducing physical gaps in the route, a warning message appears. Clicking Yes will complete the route edit activity and introduce gaps. Clicking No will stop the edit activity and preserve the previous values.
The route is now realigned.