Intersection Profiles “Cannot Be Locked?”

by Russ Nicloy, Civil Applications Engineer

One of the nice things about the intersections tool in Civil 3D is that the secondary road’s profile will lock itself to the elevation of the primary road’s profile.  This has a couple of advantages.  One being that you don’t have to be terribly precise when creating the secondary road’s profile.  I’ve intentionally ignored the proper elevation just to make sure this is true - but I’m not suggesting your profiles be 20′ apart.  Also, the real reason for this is that if you make a change to the primary road profile the secondary profile will react and match that intersection point.

The issue some have had is, from time to time, they receive a message indicating that one or more of the secondary profiles cannot be locked  This is what that message looks like:

The issue that I have run into is not that you haven’t used a “fixed tangent” or “free parabola,” as the fine print of this message would seem to indicate.  I chased that one for quite a while.  The actual problem is that the secondary road profile is not able to be edited in this file, therefore,  cannot be changed to the proper locking position of the primary road’s profile.

This is probably being caused by the secondary road’s profile being a data reference from another file.  A referenced object cannot have its geometry changed, and that is exactly what this process needs.  You can check the profile in the Toolspace, and if it has a little marker next to it (screenshot below, hopefully familiar to those using data shortcuts) then it is in fact a reference.

The quick way to fix this is to promote the secondary profile.  This makes it part of the file where the intersection is being designed, it ensures locking to the primary is possible, while still allowing the changes to the primary (in a different file) to affect the secondary profile.  It only brings over a small amount of information, so you aren’t adversely affecting your file, or your workflow.  Simply right-click on the profile name and choose Promote (it also appears in the ribbon when the profile is selected).

My first concern was that I would accidentally, or need to, promote the alignment, the surface profile, or some combination of other objects.  This turns out not to be the case.