[ORD] Create Median Island - void in pavement terrain, or clipped terrain?

Question

I am working on my first test project in ORD, and I have a curbed island in the middle of one intersection. 
 I can't recall if it is better to use the outline of the median to create a void (hole?) in the pavement terrain, or if I want to use those features to clip the pavement terrain. My search insight isn't working well this morning either - I'm sure it's been discussed here before, but I'm coming up with nothing. 
 Would I have to create a copy of my features as a closed element for my clipping element? 
 The Learn Training tells me to create a void in the terrain, which is fine. I just wanted to confirm this is the best course of action from people who have done more of this than I. Thank you.

Mariusz Heczko · Accepted Answer

Hi MaryB, 
 We use Drape Void to remove part of pavement terrain. The benefit of Drape Void is that it can be applied to a string (A) that is dependent on other string (B) (e.g. horizontal offset) and that string (B) can be dependent on the terrain (e.g. has a profile from surface). 
 So if you have a complex element (B) defining the shape of the island, you can drape that string to the pavement terrain (convenient) and then create string (A) as small offset to the inside of the island and use it to create a hole in that pavement terrain (add to the terrain as Drape Void). If you have pavement surface template applied to the terrain it will also be clipped. 
 I am not sure how the triangulation is defined / controlled after applying Drape Void - I mean the density of triangles or triangles split - so it will require some testing if the actual 3d surface is satisfactory. 
 It would be interesting to hear other users' experience in using Drape Void or other methods for modelling islands.

Chris Key · Answer

MaryB, I only have experience from OpenRoads Support and not actual project design, but wanted to give my thoughts and suggestion. Other users may have differing opinions or experiences. 
 I would lean toward adding the median as a void feature in the terrain. When designing divided roads and intersections, you could end up with many areas of interest (multiple medians or islands) in which you want to clip out from the finished design terrain. Creating clipped terrains will create many copies with dependencies if you add more than 1 area. 
 If going the Clipped Terrain method, you would have to create the first clipped terrain with the first median. Then create a clipped terrain from the clipped terrain if you want to void out another area, and again if you have another area you want to void... This could essentially link/rule many terrains together and make your Civil Model convoluted. 
 If you add Void Features, you can add multiple closed shapes a Void Features into a terrain and the triangulation will be excluded from those separate areas. If you have modeled the median and you already have a 3D linear shape you can just utilize a Void as it will have correct elevations. If you just model the area of interest with a shape in plan, you could use a Drape Void so it will drape onto the terrain to associate elevations for controlling triangulation. 
 https://communities.bentley.com/products/road___site_design/w/road_and_site_design__wiki/38762/video-add-interior-boundary-feature-ord 
 https://communities.bentley.com/products/road___site_design/w/road_and_site_design__wiki/15919/difference-between-a-hole-feature-and-a-void-feature

[ORD] Create Median Island - void in pavement terrain, or clipped terrain?

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