Would you need a sensor to know when one train has come in for some down time so you could release a fresh train?
In the program I account for a switch system to check when trains have docked. As soon as the current train laps 5 times the 6th time it triggers itll start the docking process. Each time the systems switches track the system will cut the power to the line and repower once the switch has been completed. The only issue i have is i dont own a 9v track to test and tweek the program on. As far as everything else I already own what i need for a working prototype.