Question:

What is the Regression Analysis used for?

Answer:

Regression is used to help define an alignment, whether that be Horizontal or Vertical, along the path of an existing track. Regression is a best fit process whereby the new alignment geometry is defined to fit as close as possible to a collection of known coordinate points surveyed along the existing track.

The Regression tools are located within OpenRail Designer at OpenRail Modeling > Rail > Regression as shown below: