Geometry

 

If arcs are present in the Alignment, they can be precisely adjusted using the dialog box:

The arrow keys can be used to work through the various arcs and adjust the radius for each arc. If the input field is changed, a button appears with which the radius can be applied. Using the right mouse button menu on the input field, the Radius Calculator can be opened to calculate the horizontal radius.

Below the input field is indicated what the maximum possible radius can be for this arc and the lengths of the straights before and after the arc. If a radius is smaller than the test value bending radius, this is indicated:

It may be that the maximum possible radius is still smaller than the test value. In that case, first the arcs before and after will have to be adjusted to make space for the current arc, or the Alignment in Civil 3D must be extended through the grip points to allow more space for a later radius.