Vertical curves profile view

[Akbar]

Why do my vertical curves look different? They have same radius but the one on the right looks very strange!!!

[jmayo-EE]

In the Graphic Performance dialog try turning off High Quality Geometry and/or Smooth Line Display and see if that fixes the display.

[nonbeard13 · Accepted solution]

hello,

look at your k values and the difference in slope between the two locations and that is why one vertical curve is longer that the other.  Length is independent of the radii, length depends on the change in slopes.

nonbeard13

[mathewkol]

To add to what the others have said...if you would indicate what looks strange to you, it would help. The curve itself looks fine to me.

[Akbar]

The one on the left I understand showing grade tangents and PVI etc same as in the pic.

But what is one on the right showing? 

[mathewkol · Accepted solution]

I figured that's what you were looking at. I didn't want to keep guessing. So there's no issue at all. The curve in the right simply has no PVI. Well, it does if you were to extend those tangents so they intersected. Civil 3D does not require the 2 tangents to meet at a perfect point; a curve can be calculated and drawn from what you have.

If it makes you feel better, join the 2 tangents at a point, but don't feel like you need to.

The question really is "How did it get that way in the first place?". That, I can't answer. I can make it happen easily enough, but I can't say how yours got that way.

[Akbar]

Any recommendation about using circular or parabolic curves? Any advantages about using one Before another? Parabolic curves give a nice K and radius values!

[mathewkol]

You use the curve type that is mandated by the reject requirements. I've never done a road design where the curve type was not parabolic. I've heard some rail jurisdictions use circular vertical curves, but I've never actually seen it. I'm not entirely sure why roads are designed with parabolas. Maybe the math was easier to calculate elevations.

[jacob.dwyer · Accepted solution]

According to this: 

https://knowledge.autodesk.com/support/civil-3d/learn-explore/caas/CloudHelp/cloudhelp/2018/ENU/Civi...

Vertical curves are parabolic because it provides minimal inertial forces on the car travelling them. Learn something new every day.