Minecraft 1.16 | 20w10a
https://youtu.be/UzBr03m5o3o
https://www.reddit.com/r/redstone/comments/gaz44u/minecart_splitter_1wide_tileable/

This is a 1-wide tilable minecart splitter.

I could not find any splitters that were 1-wide, so I made one. I've also included 2 example uses, the 1st is a trainstation, and the 2nd is a storage system. Both examples uses a 4 bit input to determine where minecarts end up in. On the control panel of the 2 examples, you can only select one route at a time and theres a 2nd button to deselect the route so it becomes a straight path. The splitter works on a toggle, therefore you must toggle an old route before toggling a new one. This is done with my modified decoder "Decoder v2" that remembers the previous input and pulses it before pulsing the new input. Honey blocks are used on the storage version to slow down minecarts exiting a column so that they do not bunch up.

The splitter works by using 2 overlapting block swappers. 1st is a rail & trapdoor on the opposite side on the direction of travel(to stop the minecart), and the same trapdoor & an another but this time facing up and to the left. When the minecart is stopped, the trapdoor to the right will be closes and pushed above the minecart. The trapdoor will be powered from a redstone block below, opening it. When the trapdoor is retracted it can now pull the minecart to the side, dropping it to another rail. Obsidian is used as this type of block swapper works by failing to push one side, they can be replaced with any non-movable block like furnaces.