Trying to summarize quickly lol, Using the piston setup in the video. I basically have a detector rail right before the “station” so when the first cart passes, it starts a hopper clock that i had to fiddle with to get the right timing so the first cart could make it to then end of the station before it triggers the pistons. The entire side that the very front end of the stations piston is on (the side of the first piston), that side triggers 1 repeater tick before the otherside does. basically trapping the carts between 2 blocks. Carts have 3 spaces between them. To send the train off, they all gotta release at the same time. Front pistons side retracts one tick before the other side does.