Corridors: Medians, right and left turn lanes, etc. Best way to Model??

[rdisacks]

I'm trying to model a corridor with medians and resulting turn lanes (widening an existing street to full arterial). Anyone out there have a good way to model? I have been playing around with having target alignments for the edge of medians, edge of asphalt....but have not been getting the best results. We have the geometry pretty much set. Thanks

[sboon]

There must be at least a dozen different ways to deal with this.  It really depends on how you want to build your cross section and assembly.  Are the widenings generally parallel to the centerline, or do you need the widenings to follow the edges of new pavement?  Are you controlling the outside edge profiles, or just matching existing crossfall?

[rdisacks]

To further describe, the street runs east-west and we are widening the street by expanding to the south. Yes, the widenings are generally parallel to centerline. However, the left turn lanes do cross over the centerline alignment. Our controlling grade is our proposed saw-cut edge on the west bound lane, where I'm assuming we will cross-slope up @ 2% to the north edge of median......then on the south edge of median cross-slope back down @ 2% to the south edge of asphalt (across the east bound lane). Thanks

[ToddRogers-WPM]

You don't have to target JUST alignments.  You can target polylines and feature lines as well.  Good thing about a feature line is if you target it horizontally, it will follow it vertically as well if you have your elevations assigned to it.

[sboon]

If the median includes a curb then I'm guessing that you want to keep the crown line on it, so that the drainage from the turn slots doesn't get trapped.  The issue that I can see is that if you maintain fixed crossfall slopes on both sides then the entire width of the eastbound lanes have to go up and down at the intersection as the crown moves back and forth.

Another option would be to match the elevation at the inside edge of the new eastbound lanes to the sawcut line at the inside edge of the existing westbound lanes, and then let the crown "float" in between them.  Your median will have different elevations on each side but it should be easier to design and construct.

Once you have worked out the logic of your cross section design then you can think about which subassemblies you're going to use, and what targeting options you need to consider.