Hi crimsonsky,
It is possible with some routes but you have to do some checking first, for instance, if one board has a ground level of say 100M and the board you want to merge to it is at say -100m, forget it. However if the two boards are at roughly the same altitude you can add a blank board to one route and merge the other route to the blank board, then connect the tracks and do a bit of landscaping.
Cheers,
Bill69