Casual Corridors: Removing the Bow Tie

January 07, 2015 By Leo Lavayen Leave a comment

When the corners get tight with sharp bends, corridor sections will begin to cross one another. This issue is known as a “Bow Tie."



Once a Bow Tie is created, the corridor will not behave as expected and corridor commands will experience issues too.

You can correct this issue a few different ways:

  1. Modify frequency and sampling settings.
  2. Add curve to the bend (PI).
  3. Use a custom assembly in region along with gradings.

OPTION 1: Modify Frequencies

From the corridor properties or using the ribbon, you can alter the frequency along the tangents, curves, spirals, and additional points (geometry, superelevation and high/low points). If needed, you can create regions and increase/decrease in only the desired areas.

CORR2 Edit values and set extra sample points to "No"

At times this might not yield the desired results... It may create too large a gap or chamfer look at the bend.



OPTION #2: Add Curve to the Bend

Another option is to add a curve at the alignment bend (PI).



Using the Alignment Geometry Editor, you can add a curve to the bend (PI). In some cases, it can be a very small radius.



OPTION #3: New Assembly

This options requires a bit more work than just adjusting settings. It will require creating another assembly that doesn't include the overlapping subassembly(s), breaking up the corridor into regions, using the modified assembly, and finishing it off by using feature lines and gradings.

CORR6 Usually you can copy and edit the normal assembly.

CORR7 Add an extra region in the overlap area.

CORR8 Using grading tools and featureless to fill the gap

CORR9 Grading can clean up efficiently when overlapping.


The Bow Tie is a known issue. It happens due to how the corridor handles design with being perpendicular to the alignment. The above methods are just some ways you can... Work around the corners!

Tagged with Bow Ties, Subassembly, Alignment Geometry Editor, bends, frequency, curves, Tech Support, Corridors, Infrastructure, tangents, Technology, Alignment, AutoCAD, spirals, Advanced Solutions, Grading, Assembly, Software, Autodesk

About Leo Lavayen

Cary, NC Infrastructure Technical Consultant

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