Trolley On Alternate Tracks

On some episodes of Mister Rogers Neighborhood in the first series 1968-1976 and modern episodes 1979-2001 the trolley would run on alternate tracks from the Eiffel Tower to Daniel's Clock instead of in front of the castle. Why were the alternate tracks used? Did the regular tracks not work? In ``Brave and Strong'' 1706 and 1707 the trolley enters the NOMB on the alternate tracks and it goes back to Mister Rogers house on the regular tracks that go in front of the castle. I wondered what was going on.