This stream runs about 67 minutes and has no title card, so the number here comes from the playlist. The first 12 minutes are in Basket's creative world. The rest is on the Hypermine Vanilla server, apart from a quick look back at the creative world near the 50-minute mark. Runwyld is on the server early on: a line from Runwyld shows in the in-game chat right after Basket joins, and "Runwyld left the game" appears about half an hour in.
Why every other car
Last time, the sorter that checks whether a chest cart has items in it missed every other car when they came close together. Basket sets up a copy in the creative world with a button and repeaters to send two carts through at train speed. Even this small copy gets it wrong.
To see what happens inside, Basket puts a pressure plate where it can be backed onto, then opens the hopper mid-run. The first item, a button, lands in the hopper. The sword from the next cart never does. "So it grabs the first item but then actually doesn't grab the second item." The carts pass too fast for the hopper to pull from both. With one more tick between them, both carts sort correctly.
Spacing the trains out
Basket could add a device to stagger the cars at every station, but that would be "kind of a bulky thing to have." Making the trains leave further apart is easier. Under Basket Station, the line of repeaters that lets cars out of the throttle gets rebuilt as a zigzag, so there are two repeaters between cars instead of one.
Then comes a test train: chest carts lined up on the caution floor, each given an item. Every car goes down the loaded line, and they all go straight, so the length counter knows it's a long train. Basket also adds items to the timer that holds the departure switch and lengthens the wait before cars start coming out, since the trains now take longer to pass.
An engine sorter
Next, engines need pulling out of arriving trains. Basket builds another item sorter on the line: a hopper, a comparator and a redstone torch that switch the track when a cart carries the right item. For now a gold block stands in for the engine's marker. "Eventually this will be a unique block." The first wiring is wrong, so Basket rebuilds it, then loops the track so a cart passing through drops its item back into the hopper.
Along the way Basket crafts a crafting table and uses it to make another chest minecart for testing. The cart with a gold block turns off; the cart without one goes straight.
Skeleton horses in the storm
A thunderstorm rolls in, and Basket heads down to a nearby pit hoping for more horses. "I was expecting more horses." There are skeleton horses down there, and up on the station floor skeletons riding skeleton horses turn up. Basket fights them off, then clears the weather.
A shaft for empty carts
Emptying engines needs a mechanism Basket hasn't worked out yet, and a quick look in the creative world doesn't help. Basket switches to storage instead. In a far corner under the station, with the beacon set to Haste, Basket digs a shaft down to bedrock for one tall stack of empty chest carts that a redstone signal can send back up. Lava near the bottom gets in the way, and Basket clears enough of it to build across to the ladder.
A tour to finish
A viewer asks to see the railroad crossing, so Basket ends with a tour: the destination picker, a quick trip back to the receiving area, then a ride to Port Hypermine past the crossing's gates and lights. At the small rail station, Basket shows its compact sorting area, which needs the same extra spacing between cars. The credits run to the end with no gameplay after them.