Holding the Main Road Crown- An Intersection Shortcut

The fewer things I have to keep updated, the better.

So when I find a shortcut that does the job, I feel the need to shout it from the rooftops.


If you are holding the crown of your main road, you can let the TIN fill in some blanks for you instead of having a second target for the main road EOP.  The main road EOP alignment and profile are tricky to keep “dynamic” and bring in another element of editing.  Whereas, my corridor “smarts” about where EOP lives is always dynamic to my corridor, and once I rebuild the corridor and the TIN all should fall into place.

So let’s skip the whole main road EOP alignment and profile.

Here’s how:


(yes I know there is software that can help me improve the small versions of these images.  Until I figure it out, just click on each image to take you out to a sharp, full sized version)

Organize your corridor into baselines.  Think about what you need.  I am not going to go into corridor theory right now, I am assuming you have taken a stab at intersections before.  So I am leaving out how to make the transition alignments, and their associated profiles as well as how to make the assemblies with a transition lane.

So we need 5 Baselines here…. Depending on your intersection, you can usually get away with 3 regions for the Main Road instead of separate baselines. 

However in a 4 way intersection your secondary road centerline must be split into 2 baselines NOT 2 regions because a baseline with an empty station range still tries to make the feature lines that would cross through the intersection.  Boy, that is hard to say with words.  Regardless, it will smack you in the face the first time you do it and you will know what I am talking about.


 You need, in addition to your “Normal” and “Almost Normal” assemblies, two like this:


Make your regions on your Curve EOP baselines, and assign the Secondary Road Alignment/Profile as a target for the assembly with the lane, and no target for the second one. (Note that any weirdness here may be fix by reversing your alignment and coming up with mental conventions for which direction your alignment runs and which side your lane subassembly is on)


Build the surface from your corridor.  Your TIN needs a little help, but no worries.  The good news is that these edits appear to “stick” upon corridor rebuild, so you only have to do this once.


Swap edges and be sure to rebuild your surface.








  1. sega2002 says:

    hello which so my name is Sergio and I am very very interested in being able to utiizar civil 3d, I have civilian version 2007 3d, have using autocad from version 12 and used ADT very little but 3d interests muchisimo to me to learn civilian, unfortunately I am studying it by my account compiling information, segun I understand civilian 3d is based on points but I do not even include/understand or the tematica or the job stream, not if your you can help me, wanted to learn it from zero, I enter civilian 3d but not that to do, or I could put points, I obtained them from a project, it places block with atrubutos, I extracted data XYZ and passes to a file txt, despues concerns civilian and if, if they left but when comparing the coordinates with the project of where I obtained the points did not give me in the coordinates not that debi to do? algun system in special? parametros… it is a land of Mexico which I want is to put the points immediately despues superficiel the contours despues sections and profiles but I have not even been able to happen to enter points… podrias to help me with algun material that takes to me step by step… me ayudarias muchisimo if agradecere can you enough but if you cannot is no problem… I am arranged to estudir it, good I leave my mail you in case you help me: sega2002@hotmail.com that you have good day bye.

  2. mark.scacco says:

    This is a good way to save time without compromising the quality of your finished surface. Thanks for the tip.

  3. SBoon says:

    Nice trick Dana. I have just found a similar solution to a problem involving grading objects. I was trying to model a quarry design. I had to design a series of flat benches starting at the bottom of the slope, then stepping up the hillside. I started with a horizontal grading object, then attached a nearly vertical grading object to step up to the next level, then repeated the process. By the time I reached the third bench the program crashed (insert curses here).

    After several hours of messing about I finally realized that I didn’t need the horizontal grading objects. All of the benches are the same width and the steps between them are the same height. I created a feature line and offset it several times then edited the elevations to build the back edges of the benches. I recreated the near vertical grading objects then created a surface from the grading group.

    Problem solved!