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Horizontal Alignment and Basic Curves

Updated December 15, 2021

This article applies to:
  • RoadEng Civil
  • RoadEng Forestry
This Knowledge Base article is an excerpt from one of our tutorial files. The files referenced in the article, as well as the full tutorial document, are available in our Tutorial Installer.  

In the following steps, you will create a horizontal alignment by creating intersection points (IPs) with the mouse. IP editing in the Location module is similar to point editing in the Terrain module. 

To download the files used in this example, click HERE 

  1. In Location, open the Horizontal_Design.dsnx file, right-click (in the Plan window) | Add/Edit IP tool pencil.JPG.

Note: Although already displayed in this file, to get your contours to display in plan-view <Right-click> | Plan Options… |check Background box. The existing road alignment is in the background as a guide for drawing the new road. The red line is the proposed new alignment.

  1. Edit the start point of the design:
    1. Move your mouse over the existing point (red cross); note that the cursor changes to a box box.JPG
    2. Click the mouse to capture the point.
    3. Move the red cross down to where the proposed alignment leaves the existing road (the Plan window will scroll automatically).
    4. Click a second time to re-anchor the point.
  2. Zoom in and fine-tune the start point of the new alignment, so that it lies on the old centerline, just south of where the proposed road leaves the old one (Figure 1 below left).

Figure 1: Drawing the Horizontal Alignment. Image on Left depicts the Starting Point of the Alignment. Image on Right Shows next IP

  1. Create a new IP:
  1. Click with the pencil cursor  pencil.JPG (away from the existing point) to create a new point.
  2. Move the red cross to the position shown in the figure above right (approximately).
  3. Click a second time to anchor the new point.
  1. Edit your IP:
  1. Move your mouse over an IP; note that the cursor changes to a box box.JPG 
  2. Click the mouse to capture the IP.
  3. Move the red cross to a new position and click a second time to re-anchor the IP.
  1. Insert an IP:
  1. Move your mouse over a segment between IPs; note that the cursor changes to a pencil with cross pencil+cross.JPG.
  2. Click the mouse to create a new IP.
  3. Move the red cross to the desired position (not important) and click a second time to anchor the IP.
  1. Delete an IP:
  1. Move your mouse over the IP created above; note that the cursor changes to a box box.JPG
  2. Click the mouse to capture the IP.
  3. Type the <delete> key to remove the IP.
  1. Continue this process until you have an alignment similar to the one in the figure below on the left.

Note: Don’t forget Undo command, <Ctrl-Z> or undo button.

Figure 2: Horizontal Alignment Before and After Curves Applied

Adding Horizontal Curves

To create a horizontal curve, you identify an IP then you define a curve between the tangents it defines. Horizontal curves are created and edited using the horizontal curve panel. You can open a new curve panel using the Curves.JPG button in the window navigation toolbar.

Figure 3: Horizontal Curve Panel

  1. Press the Activate Horizontal Curve Panel button using the Window Tools toolbar in the lower left part of the screen (figure above).
  2. Use the Previous IP or Next IP buttons to move to the second IP in the alignment (watch the Plan window).
  3. Press Get Default Curve button to set up the parameters as shown in the figure above.

Note: The curve panel controls are disabled until the current is point is an IP between two tangents. Most of the controls are still disabled until you either select Circle or Spiral or press the Get Default Curve button .
Default curves and associated tables are stored with your template table. The default template table is Normal.TPL.

  1. Press the Apply button to create the first curve.
  2. Use the Next IP button to move to the third IP in the alignment and repeat to the steps above to create the second curve.
  3. Return to the Plan window and edit one of the curve IPs. Notice that when the IP is captured, the curves update dynamically as you move the mouse. Also notice that you aren’t allowed to overlap the curves or to push a curve off the end of the road.

Note: The current cross section is shown in the Plan window as a red cross. When you have finished editing a curve, the current cross section is the End Curve (EC) point.

  1. Go back to the curve panel and increase the radius of the two curves:
  1. Use the Previous IP or Next IP button to select a curve.
  2. Type a new radius (it must be small enough to fit or you will see an error message).
  3. Press the Apply button.

Modify the IP locations and continue adjusting the radius and see if you can get the new alignment to line up with the proposed alignment in the background.

  1. File | close. Do not save changes.

Adding Terrain Files in Background

In can be useful at times to bring in another terrain file to compare alignments or add topography. The process for adding terrain files is:

  1. Right-click… | Plan Options…
  2. Check Background box | press plus button next to background
  3. Press Add… button to add .terx or .ter files.
  4. Press Open files will show up in the background.
  5. .terx and .ter can also be removed using the remove button rather than the add… button.