trimming alignment

[cceleeds]

is there a way to trim an alignment?

i have one drawn up but need to shorten the road and none of the posts I've seen so far have helped me.

I'm not sure if it might be a problem with the drawing.

[Jay_B]

Not sure what you mean by "trim alignment"?

There is not Trim Alignment command per say. The options I'm aware of are:

a. Maybe you're OK with Masking and not seeing the Alignment portion you wish to Trim?

    Then use the Masking Feature within Alignment Properties, see Alignment Masks

    This is the least intrusive option and is visually similar to trimming but the portion of the alignment

    is hidden & not deleted from the overall definition.

b. The alignment can be redefined to desired start stop (which has caveats such as how far into design you might be)

    and what may be affected by redefining.

    If redefining, thought and caution must be used if Civil 3d objects are of concern such as corridors etc.

[neilyj666]

....or you can grip edit (if the geometry and other considerations) allow.

[Neilw_05 · Accepted solution]

As you likely know, C3D alignments are custom objects that require special tools to manipulate them in most cases. You access those tools by selecting and RT click or select from the Ribbon and choosing Edit Geometry. So you can't use the trim command to truncate an alignment.

Here are a few scenarios that you may encounter:

1. Your alignment ends with a tangent and you want to shorten the end to meet at a crossing line.

In this case just drag the end grip and snap it to the intersection with the line.

2. The last element of the alignment is a curve and you want to trim it to a crossing element

Depending on what type of curve you applied to the end of the alignment you may be able to grip edit the end and the arc will shorten while maintaining it's radius. If you don't have that type of arc then you can either replace it with one that does OR you can adjust the constraints using the settings in this post (http://forums.autodesk.com/t5/AutoCAD-Civil-3D-General/Extending-alignments/m-p/3589806/highlight/tr... OR you can draw some construction lines with generic CAD elements and use them as a guide to grip edit the arc.

3. The crossing element leaves two or more pieces of the alignment that need to be trimmed off the end.

In this case you'll need to use the Edit Geometry tools to delete the pieces beyond the crossing element, then use the techniques in case 1 or 2.

[gordon.ray]

This thread is a little old at this point, but for anyone else who ends up having this issue, I found a solution that might be helpful. (I should note that I'm relatively new at C3D and alignments in general, so this may not be new information for many of you!)

I'm working on an alignment that we received from another company when we took over the project (it's a bus rapid transit job). The very end of the project contained a loop in a parking lot for the buses to turn around. We ended up using an alternate design, and decided to just end the alignment where the bus turns off the main corridor, so I needed to remove the loop.

Obviously the TRIM command doesn't work on alignments, but I found a command that essentially does the same thing, as long as you're okay with "trimming" an entire segment. (It looks like the answers above are for trimming midway through a segment).

To delete segments from an alignment:

1. Select the alignment
2. Alignment Tab > Modify Panel > Geometry Editor
3. Select the "Delete Sub-Entity" button
4. Select any lines/arcs that you want to delete

Again, this may not be new information for many of you, but it took me a good bit of Google searching to find that, so hopefully it helps somebody!