2.0

Chapter 4 Working with Cross Sections
372
Example of Superelevating Complex
Compound Curves
In complex compound curves, there is a combination of alignment entities
between curve 1 and curve 2. This situation may occur during the design of
complex highway exit ramps where curve 1 and curve 2 are separated by a
spiral-tangent-spiral.
You can superelevate a complex compound curve by modifying the End Station
of curve 1 and the Start Station of curve 2 to match a common station within
the spiral-tangent-spiral.
For information on superelevating compound curves, see Example of
Superelevating Compound Curves Separated by Tangents or Spirals in this
chapter.
Superelevating Reverse Curves
In order to superelevate reverse curves, the end station of curve 1 must equal
the start station of curve 2. When these stations match, Runout and % Runoff
are ignored and a 0% cross slope is applied at the point of reverse curvature,
where curve 1 meets curve 2.
To superelevate reverse curves
1 From the Cross Sections menu, choose Design Control ä Superelevation
Parameters to display the Superelevation Control dialog box.
2 Select the Superelevation calculations check box to superelevate the cross
sections.
3 Click the Edit Data button to display the Superelevation Curve Edit dialog box
for curve 1.
4 In the Curve Edit Information section of the dialog box, edit the superelevation
data.
For more information, see Editing the Superelevation for One Section At a
Time in this chapter.
5 Under Transition In, enter values for Runout, Runoff, and % runoff for curve 1.
6 Under Transition Out, do the following for curve 1:
n
Set the Runout to 0.
n
Set the Runoff to a runoff distance of your choice.
n
Set the % runoff to 0.
NOTE
Autodesk Civil Design ignores Runout and % runoff at the point of reverse
curvature. Therefore, it is better to set these values to 0 for the sake of
clarity.
7 Click the Next button to display the Superelevation Curve Edit dialog box for
curve 2.
8 Repeat step 4 for curve 2.
9 Under Transition In, do the following for curve 2:
n
Set Runout to 0.
n
Set Runoff to a runoff distance of your choice.
n
Set % runoff to 0.