Yes, this is possible. Using the OpenRoads Start Station command, the prompt sequence is:
- Pick the alignment.
- Set a position along the alignment where you wish to define a definite station value. You would pick the location where 0+00 occurs.
- Define the station at the selected position. You would enter 0+00
OpenRoads then defines 0+00 in the middle where you pick with negative stations one direction and positive stations the other direction.
WARNING: I recommend doing some testing with the workflow after the stationing is assigned. For example, do some profiles and some corridors and etc. to make sure everything behaves. I offer this warning not because it know it will fail but because I don't know for sure. Since negative stationing is outside the norm of everyday practice, it is possible that a bugaboo lurks which has not yet been exposed.
WARNING 2: Since you are using GEOPAK. There are some known issues (I don;t think these were ever all fixed) in the legacy GEOPAK tools. Therefore, if the alignment will eventually be exported to GPK for use in plans production, I think you can expect problems.