Reverse Curves

Is there a way in InRoads to create a reverse curve without having a tangent in between the curves?

Example, I am making a 400' (radius) curve that goes to the left and has a 400' (radius) curve that goes to the right with no tangent.  It is making an "S" shape.

When I create this layout in MicroStation I can import the alignment by going File -> Import -> Geometry -> From Graphics and selecting the Horizontal Alignment from the drop menu.  I use the "Check Integrity" of the alignment to make sure it is in right. But this is a hassle to do once the alignment is already created and you are making changes to it.

Once I have the alignment already loaded and try to make an "S" curve it gives me "Solution overlaps or contains discontinuities".  If I make my curves have a 399.9' radius then it will work with a very small tangent in between, but I don't want any tangent I want an "S" shape.  Any solution??  Hopefully that makes sense.

•  Hi,

You can use Multiple Horizontal Element Regression Analysis to acomplish this task. You may need to activate this tool from (Tools/ApplicationAdd-Ins). To create reverse curve select the first and the last tangent element and and add two curves between. Choose free parameters and enter  'first guess' values for curves lengths.Hit Apply and Inroads will compute curves for you. This is really powerfull tool.

good luck.

There is also the Horizontal Element Tools these tools give you full control over the elements allowing the creation of compound curves. Below is an explanation of some Geometry Layout Methods.

Mike Longstreet
Vermont Agency of Transportation
Civil Engineering Technical Support

Another alternative is the Horizontal & Vertical Elements Application Add-in. It must be InRoads or InRail for this to be available.

With these tools, you can build all sorts of compound and reverse curves. Once your tangents are in place, use the Place Free Curve tool. It's the InRoads equivalent of the Fillet tool. Radii are either + or - so if the first attempt seems to go the wrong direction, try the opposite sign. Sometimes you have to use the check integrity tool to re-order the elements or to occasionally reverse the direction of elements.

These are powerful tools worth learning - including the vertical elements tools.

• MicroStation user since IGDS!
• Dragged kicking and screaming into the world of Civil 3D, too!

In the New Geometry tools to be released with Select Series 1, you can do this.  There is a reverse curve tool in which one of the lockble inputs is the tangent length.

Naturally, Radius1, Radius2 and Tangent length are interdependent and locking two of them will require that third adjust if the reference elements between which the reverse is built are parallel.

If the based elements are curved or non-parallel, then it might be possible to lock all three and still get a solution.

Robert Garrett
Senior Product Engineer
Bentley Systems Inc.