Creating a Dirt Road? Corridors Are NOT Overkill!


Some people I have talked to have tended to shy away from using corridors for modelling certain things that they thought corridors would be “overkill” for. One of these things I am referring to is just a simple dirt road, with maybe a berm and/or a swale on either side. People tend to look at the lane sub-assemblies and other similar subassemblies saying, “but I am just moving dirt! I don’t need pavement and don’t want to have to sit there subtracting the pavement thickness to get my finished surface!” Wow!  Ok! While I can understand your concern for trying to keep it simple, the tools you are looking at are already complicating what could be a very simple process. By using Generic subassemblies in Civil 3D a dirt road can be created very quickly and efficiently. In this blog I will show you a very basic example of creating a simple dirt road using only content from the Generic Links tab in Civil 3D 2012.

In this example, I am going  to use three subassemblies (two are the same type) per side to accomplish the following:

1. create a two-lane dirt road

2. create a berm on either side of the road

3. daylight to the existing surface in cut or fill condition.

That’s correct! Only three generic subassemblies on each side to accomplish all of that quickly and easily. Figure 1 below shows what was used to create the assembly.

Figure 1 - Assembly

Figure 1 - Assembly

The three subassemblies used from the Generic tab in Civil 3D were as follows:

1. Link Width and Slope for the lanes

2. Link Width and Slope for the inside of the berms

3. Link Slope to Surface for the outside of the berms that will daylight to the existing ground surface.

With the assembly completed, and the alignment and design profile created, the corridor and finished road surface can now be created. The completed corridor and finished surface can be seen below.

Figure 2 - Corridor

Figure 2 - Corridor

Figure 3 - Finished Surface

Figure 3 - Finished Surface

You can see how the corridor moved dirt to get our road surface created quickly and easily. Also, notice how the daylighting toward the end of the corridor went into a more extreme fill situation based on the elevations of the design profile daylighting to existing ground. Obviously with everything being linked, edits made to any of the elements will be dynamic. With all of this said, if you haven’t tried them, consider using the Generic Subassemblies in Civil 3D and you will see how quickly and easily you will be able to create your corridors and surfaces with them.

Civil Infrastructure software is my main professional interest. Civil 3D, Infraworks, and Recap are what I work with mostly. I have been with CADsoft Consulting for over 10 years now. I got my start using Softdesk and AutoCAD R12 in DOS. My wife and I have four children and I am a die hard Red Sox fan.