secondary channels toolbar, click the 
Delete Secondary Channel button.
This option is to delete a Secondary Channel.
On the secondary channels toolbar, click the Delete Secondary Channel button.
You can now select which secondary channel to delete. As you move the mouse over the drawing the secondary channel closest to the cursor will highlight. Click the mouse to delete the highlighted item.
Your road will then be recalculated to use the new design in both 2D and 3D, and any other aspect of the design (for example a nearby junction) will be automatically recalculated to accommodate the changes.
Note: The deletion can be reversed by using the Undo facility.