How to model corridor from edge toward centerline

[Neilw_05]

I brought this idea up in the not too distant past but I want to query the corridor gurus to hopefully find a way to make it work.

When a corridor has lots of variations along the outside edges of the travelway it can make corridor modeling from the centerline a cumbersome task. This is because we have to create a template and region for every scenario where the edge treatment varies from right to left.

To simplify the process I have considered creating alignments for the edges of the roadway and adding them as baselines to the corridor. This way we can create just a few assemblies for the various edge treatments and apply them independently to the left and right baselines. These assemblies would then target the centerline profile to model the crown of the roadway, just as we do for curb returns.

In my experiments it seems to work nicely, but I encountered problems when viewing cross sections and calculating quantities, since the software is designed to work from the centerline baseline. Would it make the sections work if I add an assembly to the center baseline with short segments of pavement and stretch them to the edge baselines?

Another challenge is generating the profiles for the edge of the roadway to use for the baselines. These profiles would need to follow the centerline at a given vertical offset to provide the desired crown slope. Any edits to the centerline profile would need to be reflected in the edge profiles. This could be done by creating a surface from a grading object that is built on a featureline generated from the centerline and using that surface profile for the edge of roadway baselines. Another would be to stretch the center assembly to the edge and generate a profile that way. I experimented with that idea but couldn't figure it out. I'm looking for other techniques here as well.

So my question is: can this workflow be made to work somehow? What ideas do you have?

Neil

[BrianHailey]

Neil,

I would go with the centerline assembly and then simply target the edge of asphalt polylines or alignments. You can target multiple alignments and polylines from the same subassembly.

If you need to create offset profiles for the flowlines, check out SincPac, it has a profile linking tools.

[Neilw_05]

Hi Brian,

Could you elaborate on your workflow? How would I set up the corridor? I think I have the idea but it would help to have an experienced hand to guide me.

Thanks

[castled071049]

Let me ask you what kinds of variations are we talking about? Is it just width and possibly vertical changes? Or like lots of driveways, parking bays, etc.?

[Neilw_05]

Castle,

There are parking bays, driveways, offset intersections, variations in sidewalk widths or no sidewalks, places with daylighting and no daylighting to name a few. What did you have in mind?

[auzzie2776]

I agree with the centerline alignment and edge profile. mainly because its the edge of pavement profile thats important. The edge of pavement profile needs to be located above the seasonal high( here in florida its 3' for fdot). also you can apply design criteria to that profile.

cheers

jason

[Neilw_05]

I was wanting to use the CL profile to control the roadway but it could be done from the edge as well. You would still need a CL profile in cases where the roadway lanes varied in width on either side. Otherwise the lane assemblies would not meet in the middle.

[nostupidquestions]

i know what you mean about it getting complicated with so many variations. we recently did a road with lots of intersections, driveways, ditches, variable with asphalt, etc. i waited as long as possible to get the cross sections created so that most of the design would be finished and i wouldn't have that much to redo. i had a crapload of assemblies to fit all the different situations. i broke them up into left and right sides which helps quite a bit and i tried keeping the naming simple and easy to understand so that when i came back to it i wouldn't have to rethink the whole thing.

[Neilw_05]

Ditching is another part of the mix.

Think about how much easier it would be if you could apply one region for the travelway and then have independent regions and assemblies along the edges. That is what I am aiming for.

[keithknifer]

I think you just nailed it.  Build the travel way first with the appropriate cross slope.  Then create alignments and profiles from both ETWs and keep them dynamically linked.  Then have at it with the necessary assemblies.

[Neilw_05]

Getting the edge profiles is what I am looking for. How do I generate them from the travelway region(s) of the corridor? Won't I end up with circular references (i.e. parts of the corridor depending on itself)?

Also what will I get when I run cross sections and quantities using this technique? I haven't had time to experiment so I'm hoping someone can tell me if this can work before I start putting time into it.

[Neilw_05]

Generating alignments and profiles from the ETW featurelines of the center corridor region does work. Adding the edge baselines and assemblies makes the corridor function as desired. However the edge assemblies do not show up in section views. This is where I got stuck before.

P.S. Well after looking closer I see that the extracted alignments and profiles are not dynamic to the centerline so it is not a solution. My next idea was to create offset alignments from the centerline at a distance equal to the width of the lanes and use these as baselines. For the profile of these offset alignments I created a surface from the center region of the corridor and sampled it for each of the offset profiles. As I suspected would happen, when I use these profiles for the edge baselines, the corridor goes into an endless loop of rebuilding.

[keithknifer]

Its been a while since I've done it, but there should be a check box when you create the alignment to keep it linked.

[andrewpuller3811]

What about a link width and slope from the center to the outside, then work you way back in?

Then set "Omit Link" to yes.

This will allow you to control the outside edges from a central profile.

[castled071049]

As for sidewalks, we don't model them in our corridors for the reasons you mention, i.e. too many variations. We use an underlying xref with sidewalks and other non-essential-to-the-model items drawn in. That saves a lot of time. Intersections are always done with the Intersection Wizard, which is a great time saver. 

Parking bays I have had partial success by attaching a LaneOutsideSuper section to the ETW of the main center assembly that targets an alignment following the parking bay. Where there is no parking, the attached lane is zero length. When bays appear, the attached lane assembly grows out to follow the alignment, then returns to zero as the bay recedes farther up the road. The problem here is that curbs look funny at the bay radii because they remain perpendicular to the centerline alignment. An offset assembly would fix that, but you need a separate profile for them and that starts to add time back into the process. 

Ditches are a problem where there are lots of driveways (and, hence, culverts), as are driveways themselves. I usually model the driveways using feature lines, not assemblies. Ditches are assemblies, but as always you must start and stop them often, which means lots of regions until they come up with a better idea, like yours.

[Neilw_05]

Andrew, I'm not grasping your suggestion. Could you elaborate on how it works?

[Neilw_05]

Keith,

I don't see any option to create dynamic links when extracting alignments or profiles from a corridor. It would solve part of the problem if we could.

[Neilw_05]

Castle,

While you guys may be able to get by without including sidewalks in your corridors, I find it necessary as there is often grading beyond the sidewalks that needs to be tied in, or we need to find daylight from the back of the sidewalk. I suppose we could use gradings from the back of curb instead, but if we can find a way to make this approach work it would be relatively easy to include sidewalks.

[keithknifer]

Neil,

Maybe I saw it when creating Feature Lines from the corridor.  I used to use that when building intersections the old way.  I thought the same applied to alignments and profiles created from corridors. 

In the past I have submitted a wishlist item to be able to use FLs as baselines in a corridor and have assemblies follow them just as if it were an alignment and profile.  I haven't dug into 2011 yet, but I haven't heard of anything new like that being added.  It would do the trick if you could.   There has to be a way to keep it linked.

[Neilw_05]

Now that support is added for showing multiple baselines in section views and also dynamic offset alignments, I would like to revisit this concept. I think it should work but I haven't had time to investigate. Does anyone foresee any show stoppers? I'm not sure how this would work with intersections or in superelevation scenarios.