I'm trying to understand precisely how the logic works for the spots in pipeline where the two tracks cross. This is mostly me thinking out loud, but if I'm understanding it wrong, please help me. For each color, there are three logic_relays: blue_crossover_relay blue_crossover_stop_relay (starts disabled) blue_crossover_relay2 (repeat for red) When the blue cart hits the last track point before the crossover zone, these things happen: blue_crossover_relay is triggered red_crossover_relay is killed blue_crossover_stop_relay is triggered red_crossover_stop_relay is enabled When blue_crossover_relay is triggered these things happen: The cap area around the bomb is disabled The red_crossover_relay2 is killed The blue_crossover_stop_relay is killed The train starts moving forward on its own Here's my first confusion: The path TRIGGERS blue_crossover_stop_relay. It ALSO triggers blue_crossover_relay, which KILLS blue_crossover_stop_relay. Why are we simultaneously killing and triggering something? Continuing the dissection: As the train moves forward, it eventually hits the path AFTER the crossover. This triggers blue_crossover_relay2 When blue_crossover_relay2 is triggered, these things happen: The cart stops moving under its own power. The cap area around the blue cart is reenabled The red_crossover_stop_relay is disabled The capture point around the red train is enabled When the red_crossover_stop_relay is Enabled, it waits for the red train to hit the final path before the crossover zone. If the train arrives, it disables that train's cap area. So to put it in plain English (I think): If the blue train hits the crossover area first, the cap area on the train is shut down, and it is automatically pulled forward across the zone. Simultaneously, the corresponding entities on the red side are killed, and the stop relay starts watching for the red train. If it arrives, its cap area is disabled. When the blue train reaches the far side, it stops moving under its own power, its cap area is reactivated, and the red train's cap area is reactivated. By this time all of the other relays on red's side have been killed. Is this about right? If so, why does the blue_crossover_stop_relay get triggered by the approach of the BLUE cart? All it does is disable the blue cart's cap area, and the blue_crossover_relay is ALREADY doing exactly the same thing. I know all these entities are probably in ABS' library, and I can just cut-and-paste, but I really want to understand what's going on.