Where corridor tangents intersect at a corner, and where the corridor is created at a fixed width, the inner and outer corners of corridors are cleaned up automatically. In other situations, such as when the corridor is created at a non-fixed width (such as when daylighting to a surface) or when there are curves in the corridor baseline, you may need to clean up the corners by extracting a dynamic feature line from the corridor and then grading from the feature line.
The AutoCAD Civil 3D 2017 corridor cleanup behavior is applied in the following conditions:
In AutoCAD Civil 3D 2017, where corridor tangents intersect at a corner, and where the corridor is created at a fixed width, the corners are cleaned up as follows:
The point where the inner corners meet is calculated and radial lines are extended from that location, using the insertion frequency along the baseline as defined in the Frequency to Apply Assemblies dialog box.
In addition, one station is also added at the corner:
The subassembly width value is overridden at the radial stations; the width is calculated to produce a corner solution that is similar to the AutoCAD Offset command.
The AutoCAD Civil 3D 2017 corridor cleanup behavior does not currently apply in the following conditions:
For example, in conditions where curves are present at the corner, the corridor may be created with sections which cross each other at the corner.
For example, if the feature line starts and ends at a corner, as shown in the following illustration on the left, the corner cleanup does not get applied.
To work around this, it is recommended that you draw the feature line so that it starts and ends at a location other than a corner as shown in the following illustration on the right.
To resolve corner issues, you can extract a dynamic feature line from the corridor and use the grading tools to grade from that feature line. The following is an example of adding grading to the right side of the corridor.