Autodesk CIVIL3D - CIVILDESIGNCOMP 2007 SLM CD Tutorials Manual page 547

2 Select the corridor that is in the intersection area.
3 Select the grip that is at the bottom of the intersection. Drag the
grip down. Click to place the grip several hundred meters to the south.
4 Click Corridor tab
drop-down
5 In the Corridor Properties dialog box, on the Parameters tab, click
Select Region From Drawing.
Exercise 3: Creating and Editing a Corridor in the Intersection Area | 535
Modify Corridor panel
Corridor Properties.
Corridor Properties