Reverse loops in 2 rail AC and with Legacy or DCS are really simple. Electrically isolate the reverse loop section of track and power it through a PSX-AR-AC Auto Reverser Board and just run the trains as normal. Does not matter how many reverse loops there are, just use one Board per reverse loop. My layout has 4. Similar with DCC , but the part number for the Board is different.
Straight DC is a PITA because the polarity determines engine direction so just instantaneously flipping the power connections to the block the engine is occupying will not work. The polarity of the block the engine is about to enter must be reversed. Ok if there is only one train running, not so good if there are already engines running in that block.
