Horizontal geometry for alignments can be described using lines, curves, and spirals.

For spirals, the following are supported:

• Clothoid

• Bloss

• Cubic Spiral

• Cubic parabola

For single carriageway/track alignments, the horizontal alignment must occur within the pavement/ballast extents.

For dual carriageway/track, the horizontal alignment must occur within the center median. For dual carriageway/track alignments, the alignments can’t have variable relationships (vertical or horizontal separation). If alignments do have variable relationships they will have to be modeled by importing the carriageway/tracks independently.

Horizontal geometry is expected to not have any alignment breaks or gaps. The alignment is expected to continue through bridges and tunnels and station equations are not supported.