Re: Why a turntable?

The key to this was that both the uphill and downhill grades were "upgrade" from the turntable. The engine would pull the cars over the crest when ascending from below, so that the cars would roll by gravity. The uphill side was of course "downgrade" the whole way.

The locomotive would cut off, turn on the table, then run out on the table lead track to the switch, and turn off on the appropriate leg. The switch was realigned, and the cars would roll down through the turntable and partway onto the tail track. The table would not be turned. The loco then backed down and hooked up.