When To Use Add Vertical Regression - Vertical Alignments Regression Point Option.

Hi all

I was wondering if someone explain the Add Vertical Regression Point Command specifically the Vertical Alignments Regression Point Option.

The Add Vertical Regression Point menu has several options:-

1) Co-go Points                                                          

2) Horizontal Alignment Cardinal Points

3) Horizontal Alignment Regression Points

4) Vertical Alignment Cardinal Points

5) Vertical Alignment Regression Points

I understand how and when to us options 1-4 but I am struggling how you would use option 5 Vertical Alignment Regression Points - it does not make sense to me because if I have a Horizontal Alignment which contains Regression Points and i have designed it.

I than create an empty vertical alignment and use the Add Vertical Regression Point menu and select option 3) Horizontal Alignment Regression Points as this allows me to copy the regression points from the Horizontal Alignment which includes the stationing into my new empty vertical alignment which I can than design.

So understand circumstances would option 5) Vertical Alignment Regression Points be used?

Thank.

S. Souten.