The Trainz plus is a different program now from Trainz22. Go to My Trainz, then on the left column, you will see a link for downloading Trainz Plus. Select that, choose which OS and what installer you want.
once installed you can point the game to use the current user directory or keep the default user directory. If you point it to your current directory, it will have all you routes. It is recommended that you backup your user directory before doing this. Don’t have different games pointed to the same directory as that can cause problems.
