Realigning a route

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. Many 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.

The Realign Route activity makes realigning your roadway a simple process. You select the data elements that represent your attributes and your geometry and apply them to the new route. Behind the scenes, Esri Roads and Highways applies your attributes and geometry to centerlines and the centerline sequence table (see Data in the ALRS for more information about the data elements in Roads and Highways) to reconstruct and calibrate your route change.

Roads and Highways uses redlines and source geometry to perform realignments. While the use of a redline is optional, the use of source geometry is not.

The more difficult aspect of editing a highway is correctly capturing the new roadway features that will make up the highway change. Complicating matters, these features are often duplicated by editors from different agencies, making it difficult for a data user to know which geometry is authoritative and accurate.

Roads and Highways puts the burden on the linear referencing system (LRS) editor to identify the correct geometry for any given highway change so that one and only one source is used to capture the alignment of the road. Since source geometry may come from sources outside of the GIS, Roads and Highways allows you to select source geometry from ArcGIS feature classes, shapefiles, or computer-aided design and drafting (CADD) files.

Note:

You should never edit directly into the centerline feature class, as this may corrupt your LRS Networks.

Steps:

1. Start ArcMap and set up your editing environment for using Roads and Highways.
2. Use the ArcMap navigation tools to zoom to the location of your alignment change.
3. Click the Networks drop-down menu on the Roads And Highways Editing toolbar to choose the LRS Network layer you want to edit.
4. Click the Activity Type drop-down list on the Roads And Highways Editing toolbar to choose Realign Route.
5. Optionally, if you have a redline feature, use the Select Redline Features tool to choose the redline for your new route.

   Choosing a redline feature is optional. You may elect to skip this step, but you will have to enter the route and measure information on the Realign Route dialog box later.

6. Use the Select Source Geometry tool to select the source geometry for the new alignment

   If the redline and source geometry are very close together, you may need to turn off the display for the redline in the table of contents before selecting the source geometry. Otherwise, you may get unwanted redline features in your source geometry selection.

   
7. Click the Apply button .

   The Realign Route dialog box appears. Values on the Realign Route dialog box are autopopulated from the selected redline.

   If you did not select a redline or the redline was missing attributes, the parameters on the Realign Route dialog box need to be manually entered.

   1. Enter an effective date for the alignment:
      • Manually enter a date in the Effective Date field. Acceptable date formats include M/D/YY, MM/DD/YY, or MM/DD/YYYY.
      • Click the calendar drop-down menu and select the alignment date from the calendar.
   2. Enter a Route ID.
   3. Enter the parameter From Measure:
      • Manually enter a From Measure.
      • Click the Select From Measure tool and click the map at the location of the from measure.
      • If you do not know the From Measure, you can let Roads and Highways suggest the From Measure. The From Measure is calculated as the source geometry length minus (-) the To Measure.
        1. Enter a parameter To Measure.
        2. Click Calculate.
   4. Enter the parameter To Measure. There are many ways to calculate the To Measure as outlined below:
      • Manually enter a To Measure.
      • Click the Select To Measure tool and click the map at the location of the from measure.
      • If you do not know the To Measure, you can let Roads and Highways suggest the To Measure. The To Measure is calculated as the source geometry length plus (+) the To Measure.
        1. Enter a parameter To Measure.
        2. Click Calculate.
   5. Enter the split From Measure:
      • Manually enter a From Measure.
      • Click the Select From Measure tool and click the map at the location of the From measure.
   6. Enter the split To Measure:
      • Manually enter a To Measure.
      • Click the Select To Measure tool and click the map at the location of the To measure.

   
8. Verify the Effective Date, Route ID, From Measure, and To Measure parameters of your new alignment are correct.
9. Determine whether you want to recalibrate your route downstream and check or uncheck the Recalibrate route downstream check box as appropriate.

   Roads and Highways assumes that the measure values you enter take precedence over the measure values that already exist on the route. This can create an undesirable effect if the measure values entered create logical gaps or overlaps in route measures. In our example, the from measure of the redline feature is less than the measure of the actual location the original route will be split.

   

   By permitting this, we are saying that location 15.9126 has an incorrect value and the real measure at that location should be 15.5908. This is common since roads are often remeasured when a new alignment is added. Roads and Highways places a calibration point at the intersection of the new and original alignments and adjusts measures along the route the first calibration point encountered prior to the realignment. Events follow their Calibrate Route behavior.

   If you choose not to calibrate downstream, you may run into even more issues when logical gaps or overlaps are created, since downstream measures are not allowed to change. By choosing not to recalibrate downstream, you are overriding the derived measures of the route. Some calibration will happen to your route in the immediate vicinity of the realignment, however, because failure to recalibrate could otherwise break the rule that routes must have strictly increasing or strictly decreasing measures. The following rules are applied when you realign without downstream calibration:

   • If the to measure of the new alignment is less than the split measure, the route calibrates using the new alignment length up to the split location. The original measures are used from the split location on. In our example with a to measure of 16.3168 and a larger split measure of 16.5909, two calibration points are placed at the intersection and there is no physical geometry for a measured length of 0.274 miles.
   • If the to measure of the new alignment is greater than the split measure, the route is recalibrated to the first downstream calibration point encountered. All subsequent measures are retained. Events between the new alignment and the first calibration point follow their Calibrate Route behavior.

10. Click OK.