Corridor Transitions vs Targets

[AllenJessup]

I'm old fashioned. So I've tended to use targets to control corridor widths. This time I used a couple of transitions and thought they worked well. So I'm trying to use them for the whole corridor. Being, shall I say, Cautious. I wanted to have a check on the transitions. I took the polylines drawn for the EP in the design plan, copied them to another drawing and turned them into alignments. Then I DRefed them into the Corridor drawing so I could display them in the section editor. That helped me pick up some errors I had made. However.

There are areas controlled by transitions that do not match the alignments created from the EP. Mostly a couple of inches but a couple of feet in some cases. I can understand some differences where the transitions occur in curves. Its Difficult to draw curve transitions knowing only the width as each end of the transition.

My question is: Has anyone done such a comparison and did you find it was better to hold the transitions in the Corridor rather than drafted polylines?

[cody.faltin]

I have found the transitions to be of limited value.  While I haven't conducted the same side by side check that you describe I have found that they have some limitations.

1. If you have a subassembly that only has vertical components, it is difficult to select the subassembly to start the process of creating a transition.

2. Transitions do not bridge over region boundaries well if you need to bridge over a region boundary.  For instance when building corridor in a complex urban environment.

My personal workflow has been more to utilize feature lines, or offset alignments and profiles to generate my target geometry.

[AllenJessup]

Yes. But for some reason I seem to be invested in making the widenings work. I may revert to Alignments for targets. Even then, I'm going to want to find out where the discrepancies come from to verify I created the Polylines I used for the Alignments correctly.

[m_kingdon]

I have dabbled with the transition tool and I do find it useful for certain tasks.  Particularly for some grading tasks where I want to adjust a LinkWidthandSlope or LinkSlopeToSurface grades.  I also use it for modelling dropped kerbs. i.e I model a continuous kerb using UrbranCurbGutterGeneral and use the corridor transition tool to adjust the A and G values to transition the kerb from full height to dropped height and full height again.  A bit laborious but the results look great.

I still use Offset Alignments to control my road widths and cross slopes.  I also find the limitations @cody.faltin mentioned frustrating.  It feels like the transition tool isn’t quite finished yet.  A more complete interface, ability to transition over regions and better selection options are needed.  I also want more transition methods.  It is annoying that Offset Alignments have some transition options whilst Corridor Transition has option.  I wish they could both share so we have all the options in both tools.

As for a workflow comparison against targeting polylines.  I can’t help you with that as I never use polylines as a target.  I personally avoid using polylines.  My personal philosophy is that corridors should be self-contained objects and only interact with alignments and surfaces.  The idea of a corridor interacting with something as loose and unhinged as a polyline scares me.

[fcernst]

Sounds like tesselation ..and frequency …and resolution issues …that need to be assessed for desired end resolution. 

[tcorey]

I like targets for width adjustment. I like Transitions for changing other assembly parameters. This feature makes very quick work of fitting dropped curbs into a design, for example.

---