Join Eric Chappell for an in-depth discussion in this video Understanding the task, part of AutoCAD Civil 3D: Intersecting New Roads with Existing Roads.
- Before we begin learning how to design the intersection between a new road and an existing road, let's talk a little bit about exactly what we're doing. If we look at the drawing here in front of you, we've got a plan view on the left and a 3D view on the right. And what we have is an existing road running north and south, and we've got a new road coming in from the west and tying in to the edge of the existing road. If you look at it in the 3D view, what you see in gray is the 3D representation of the existing terrain, and you can see the road surface defined quite well in there, and the colored area is the new road, the corridor coming in from the west.
So what's challenging about this design, is that we're tying in to the edge of an existing feature. Existing means real-world, and lines aren't straight, slopes aren't constant, it's an irregular shape in 3D that we have to tie in to. But we have to do it well, so that we have a smooth transition of traffic from proposed to existing and the other way around as well. This all has to be a nice, smooth pavement surface in this intersection area. So that's the challenge we have in front of us and there are a couple of key areas that we'll need to address.
One is this actual edge, or this seam, where the new road meets the existing road. That's gonna be a tricky part of the design to actually nail down. We've also got this transition area here called the curb return. And here we have to transition from existing slopes and elevations to proposed slopes and elevations, and that needs to be a nice, smooth transition on both sides. And then we also have the point here, this is a key point, where the two road centerlines intersect. You can see it here in 3D, and here in 2D, where the green meets the red.
The green is the proposed centerline alignment, and the red is the existing centerline alignment. So those are the key things we're going to be looking at as we progress through this design. So now that you can visualize what we're aiming for go ahead and watch the rest of the videos, and learn how to leverage Civil 3D to build this for yourself.