raised median in corridor

[pmuron]

I have a baseline profile as a finished grade of a roadway corridor and want to add raised medians within a portion of the corridor.  Any suggestions as the best way to have the medians adjust as the profile grade changes?

[Joe-Bouza]

Maybe build it into your assembly or maybe extract TC feature lines and build it with a grading.?

[castled071049]

If you build the median with your assembly, you still have to deal with the rounded ends of the medians using feature lines or some other means. If you adjust your profile, the main median will adjust with the corridor accordingly, but you will have to redo your two rounded ends again. One profile change = two re-dos per median.

We do not include the median in our assemblies. Rather, after we have built the median-less corridor, we take the underlying polyline representing the median gutter flowline and turn it into a feature line with elevations taken from the corridor. We offset that 0.5' in and 0.5' up to get the BOC feature line. We add that to a surface called, say, Median 1, and paste that into the corridor surface. If your proposed profile changes, you will, of course, have to unpaste the Median 1 surface, reestablish the new corridor surface elevations for the Median's feature lines, and repaste it to the corridor surface again. One profile change = one redo per median.

It's still a little hassle, but only it takes about 2 minutes to redo a median if the profile changes. Wait until you are pretty sure the profile is where you want it before doing the median work, and you will keep the changes to a minimum. I do not know of a better way to do medians, but would love to hear about it if someone knows one.

[jeff_rivers]

I haven't built a median in a corridor, but assuming the median is a constant width, could one use offset alignments to get the left & right sides, then an offset profile to get the elevation at the centerline, and then make an assembly using link-width-and-slope subassemblies to target the offset alignments? 

By using offset alignments and profiles, it would be dynamic to the design profile & alignment.  It's been a while since I've worked on a roadway corridor though, so I could be forgetting something...

[castled071049]

Yes, but you are still left with the problem of modeling the rounded median ends. I know of no better way than to use feature lines for these, which would not be dynamic to the corridor changes. So... just make the whole median a simple feature line surface and make changes accordingly. No offset alignments, profiles, etc.

Again, this is our way of handling medians, not necessarily the best, but would love someone to prove us wrong.

[dgordon]

either in 2011 or 2012 they made it so feature lines extracted from the corridor could be dynamic to the corridor and change with it.

[castled071049]

One can extract dynamic feature lines, but only from feature lines built into the corridor assembly. (e.g. EOP, TOC, etc.) And, you cannot trim or otherwise edit them to fit a median that may vary in width or have turn lanes, gaps for cross streets, etc. And, as mentioned before, you still have the problem of dealing with the rounded ends of the medians, which will require non-dynamic feature lines.

Which brings me full circle to just create feature lines from elevations from the non-median corridor surface, add them to a median surface, and paste it into the corridor surface.

[mathewkol]

Notes for the OP.
The technique above works very well but you may have problems pasting a median surface into the actual corridor surface. It's safer to paste the corridor surface into a "Composite" surface and then paste the median surface into that one.

Another place where you may have trouble is if the median is quite wide. If your datum surface is defined well below the median surface (especially if it's a grass median) your volumes will be off.

[castled071049]

I am wide open to a better way of doing medians. How do you deal with the rounded median ends??

[sboon]

I've been playing with this for a while, and I may have a solution.  What I did was to create an alignment that follows the outline of the median at the point where the bottom of the curb face intersects the asphalt.  I then cut a surface profile on the top surface of the road corridor and used that as the baseline for the median corridor.

The assembly is just a curb shape, and the median corridor creates a top surface from it.  I also added an outer boundary following the outside of the median.  Finally I created a merged FG surface and pasted all of the pieces together.

I found that if the alignment start and end need to have a small gap - if they are exactly the same location you can get odd results while editing the alignment or the corridor.  The nice thing about doing it this way is that the location and shape of the median are not relevant to the rest of the design.  You can create curved ends, bulbs or whatever you want -  the elevations of the median are always tied to the corridor surface that it it sited on.

[Joe-Bouza]

Kudos!

Awesome Steve! the simplicity in it's ellegance gets a big Kudos!

[castled071049]

I do like the idea and will give it some testing. One last question: A typical median goes down the centerline of a corridor and straddles both sides of a road sloping, say, 2% down away from the centerline. This creates a "peak" of sorts down the middle of the median. (Perhaps not in turn bays and other siturations, but a majority of the time.) How does your technique address this? At this time, I can only see a flat surface connecting both sides of the median using your concept.

Again, great job working out that solution!

[sboon]

I can see several ways to address the problem.

1. Add a LinkWidthAndSlope sub to the back of the curb.  Target that sub horizontally to the road centerline alignment.  This technique will work only where the curbs on both sides are at the same elevation and offset from center.
2. Another option would be to add a vertical link to the previous sub, then add a MarkedPoint to the back of the curb sub, and finally a LinkToMarkedPoint at the top of the VerticalLink.  The LinkWidthAndSlope sub is now targeted both horizontally and vertically to the road centerline.  This creates a situation where the crown of the median is always centered on the road below and the median height is fixed - the slopes will vary depending on the elevation and offset of the curbs on either side.
3. The final method is a little more tricky.  What I did was to split the median alignment into two pieces - left and right sides.  Then I copied and mirrored the curb subassembly to the end of the LinkWidthAndSlope, and then replaced the LinkToMarkedPoint with a LinkSlopesBetweenPoints sub.  The corridor targets were changed so that the LinkWidthAndSlope targets the left median alignment and profile.  The result of all this is that the corridor builds the right curb, then locates the opposite side and builds the left curb.  Finally the LinkSlopesBetweenPoints sub calculates the crown point between the two curbs using the specified slopes.  Note - the intersection may not fall within the median if the curb elevations are very different.  Since this assembly doesn`t work for the ends of the median I created another one that only has the curb sub, and added two new regions for this.

[mathewkol]

Steve. Isn't it past your bedtime?

[sboon]

Yep - us old guys need lots of rest.

[MARCFOLSOM7010]

In your method of a raised median corridor built on a roadway surface corridor are you actually building a corridor within a corridor utilizing 2 separate BL's or are you building the median corridor and dref'n the roadway surface created from the first corridor?  Using the roadway surface profile to dynamically link the median is exactly what  I am looking for.  Thanks!

[sboon]

It's two separate corridors in the same drawing.  The file is attached to a previous post - check it out for yourself.

Steve
Please use the Accept as Solution or Kudo buttons when appropriate

[pmuron]

I built the main corridor of the roadway, and then created another baseline/corridor for the median, and made them interactive with each other. If you change the original alignment and profile, then the median elevations change as well. If you need more information, let me know.

[MARCFOLSOM7010]

Both roadway corridor and median corridor are doing exactly what I want them to do with respect to creating the cross section.  My question is with respect to the surface that needs to be created by both the roadway surface and the median surface.  Are you pasting the median into the roadway or are you creating a composite surface with both.  Pasting the surfaces then rebuilding the corridor takes a very long time or even worse - it bombs out.  Please advise.  Thanks!

[pmuron]

I pasted the main alignment surface and the median surface into an overall surface. I have not had trouble with updating, other than having to update the median corridors when the main baseline alignment is updated. My project is not that big or complicated, so my regen times are not long.