Creating a Cul de Sac with a Corridor (9:20 min)

For major transportation, city roads, and land development projects, using corridors within Civil 3D can help streamline the design phase and manage change more efficiently throughout.

In this tutorial, you’ll learn a few tips and tricks in corridor modeling, specifically how to create a cul-de-sac within a corridor. For this exercise, we’ll use targeting to lay out the horizontal and vertical design as well as use additional baselines, assemblies, and target control to quickly and easily design/model a cul-de-sac.

Before we begin:

  • To begin, we’ve already created a corridor in Civil 3D. The corridor in our example is half-width, and we have an alignment and profile for that corridor as well as for the cul-de-sac.

How to create a cul-de-sac:

At this point, we need to create an alignment and profile for the yellow line in our cul-de-sac which will be our line of asphalt.

1. Under the “Home” tab and “Create Design” panel, select “Alignment” and then click “Create Alignment from Object”.

2. Select the yellow line, which is our edge of asphalt, and hit “Enter”.

3. We want the direction to go from top to bottom, or left or right, so hit “Enter” again to accept that.

4. Name the cul-de-sac, leave default settings as they are and unclick the checkbox for “Erase existing entities”.

5. Click “OK”. Now we have our alignment!

6. Select the alignment and click on “Surface Profile” in the ribbon.

7. Sample your existing ground and entrance road finish grade (our corridor) by selecting them from the top right box and hitting “Add>>” for each of them. This way, we know what to tie into at each end of our cul-de-sac.

8. Change the profile style of the entrance road finish grade to “Design Profile” by right-clicking on it under the “Style” section and selecting “Design Profile” from the drop menu.

9. Select “Draw in profile view”.

Add user specified information for the Station Range

1. In the next window that pops up, select “Next” and add user specified information for the Station Range in the next window to give us some extra padding in the profile view.

2. Click “Create Profile View”.

3. Place the profile on the right side of your screen.

4. In this profile, you can see the portions we are tying into on each side.

Now we need to create a design profile for that cul-de-sac.

1. Under the “Create Design” tab at the top of your screen, select “Profile” and then “Profile Creation Tools”.

2. Select your grid. A window will appear with settings. Leave those at the default settings and click “Enter.”

3. A tab will open up titled “Profile Layout Tools”. Select the first icon and click on “Draw Tangents With Curves” from the drop-down menu.

4. With that tool selected, tie it into the finish grade on the left side and drag it to somewhat of the center of the cul-de-sac.

5. From the center point, drag it to the finish grade on the right side. You can modify the elevations from here, if you would like.

Now we need to create an assembly:

1. Under the “Create Design” tab at the top, choose “Assembly” and then “Create Assembly”.

2. Name the assembly and click “OK”.

3. Place the assembly on the left side of the profile.

4. Now we’re going to create a simple sub-assembly. From your tool palletes on the left, select “LaneSuperelevationAOR” to add a lane. We’re going to use this as targeting, so we don’t need a full lane.

5. We want our lane on the left side to be 2 feet wide, so under “ADVANCED” and “Parameters”, change the “Side” to “Left” and the “Width” to “2”.

6. Now we’re going to add a curb. Under “Tool Palettes” and “Curbs”, select “UrbanCurbGutterGeneral”.

7. Click on the assembly to place the curb.

8. Now add a sidewalk. Under “Tool Palettes” and “Curbs”, select “UrbanSidewalk”.

9. Under “Properties” on the left and “ADVANCED” and “Parameters”, modify the planter strip to 5 ft.

10. Place it at the top right of the curb.

11. Add in a daylight condition. Under “Tool Palettes” and “Basic”, select “BasicSideSlopeCutDitch”.

12. Place that at the top right corner of the sidewalk.

  • This is the assembly you will use within the cul-de-sac corridor.

Now it’s time to build our corridor:

1. Zoom into your cul-de-sac now and choose the existing corridor.

2. Right click and select “Corridor Properties”.

3. From the “Parameters” tab in the window that pops up, select “Add Baseline”.

4. Pick the baseline from the screen by clicking on the edge of asphalt (the yellow line).

5. Click “OK”.

6. Click on the bottom line of the window and give it a vertical profile by selecting “Layout (2)” from the drop-down menu. Select “OK”.

7. Right click on that bottom line again and select “Add Region”.

8. This is where we’re going to use the curb that we created. Click “OK”.

9. Modify the beginning and ending stations by clicking on “Start Station” and clicking on the curb return.

10. Do the same for the “End Station” on the opposite curb return. Select “OK” and “Rebuild Corridor”.

11. We want to tighten up the cul-de-sac, so we’re going to change the frequency. So, click on the corridor.

12. Select “Edit Frequency” from the ribbon and change “Along tangents”, “Curve increment” and “Along vertical curves” to 5 ft.

13. Now we want to target the corridor center line of the cul-de-sac and the center line of the main road. Select the corridor.

14. Choose “Edit Targets” from the ribbon and click inside the cul-de-sac.

15. A “Target Mapping” window will appear with options to target surfaces, width and slopes. We’re going to target width of the asphalt section first. Click on “<NONE>” on the “Width Target” line.

16. A window titled “Set Width Or Offset Target” will appear. Under the drop-down menu at the top of the window, choose “Alignments”.

17. Click on the “Select from the drawing” icon and click on the center line of the cul-de-sac and the center line of the road.

18. Select “Enter”.

19. The “Set Width or Offset Target” window will appear again. Click “Add>>”.

20. Click “OK” and then click “OK” again in the “Target Mapping” window.

  • We’re not done yet! From here, if you click “Enter”, you can see that the cul-de-sac has been modeled. We haven’t yet targeted for elevation, so it might just be targeting for width. It might look good here, but we haven’t fixed the elevation based on these two profiles.

21. Select “Edit Targets” again from the ribbon.

22. This time, where we targeted the width in the “Target Mapping” window, we want to target the same center lines for elevation.

23. Select “<NONE>” on the “Outside Elevation Target” line.

24. Click on “Profiles” from the drop-down menu at the top of the “Set Slope Or Elevation Target” window that will appear.

25. Select your cul-de-sac from the “Select an alignment” drop-down list.

26. Select your finish grade from the “Select Profiles” box and hit “Add >>”.

27. Repeat the last step, but add your profile.

28. Click “OK”.

Let’s target our surface while we’re here:

1. Click on “Edit Targets” in the ribbon.

2. Click on “<NONE>” from the “Target Surface” line in the “Target Mapping” box.

3. Target the existing ground by choosing your daylight condition. Click “OK”.

And that’s how it’s done! By adding in the alignment and profile for the cul-de-sac and utilizing a simple subassembly, we can add that to our corridor and easily model things like cul-de-sacs, knuckles, turn lanes and more by using targeting!