Simple minecart RAIL systems, originating from CenturyTA. CARTS is a design for a minecart station that will allow a player to roll in (or place their minecart) onto a launch strip. The player can then press a button and be sent on their merry way to any number of destinations. CARTS will not provide minecart storage, it is just a very fancy track selection system. The station can be expanded to accommodate as many destinations as a player would be able to reach and as many as you are able to route outputs from.
How to make a CARTS station
This tutorial will show you how to make a CARTS station with five outputs, due to the design, you can add or remove the outputs to suit your needs. The instructions are written out, but as the saying goes, a picture says a thousands words, so each step has a companion image to show you what you should have so far. Each is taken from roughly the same view point, the rear right corner. Except where noted, all the repeaters are set to the default setting (one tick, shortest delay).
Woking from the front to the back, place an eight long strip of blocks, then a row of repeaters facing to the rear of the CARTS system and then another row of blocks. Next, place a zig-zag of repeaters and redstone dust facing the front of the CARTS system. Finally, place another row of eight blocks, each with a red-stone torch attached to the rear of it; these torches at the rear are the outputs that will use to control the track switching. In total, this layer should be seven blocks deep.
Again working form the front to the back, place an eight long strip of red-stone dust; this is where you take the signal from to launch the player's minecart. Next a row of blocks followed by a row redstone torches, this should be standing on the block bellow them not on the side of a block. Next, you need to place a zig-zag of blocks above the eight repeaters you placed in the last step. Where the zigzag of blocks are nearer to the front of the CARTS put redstone torches on the back-facing side. Finally, place four redstone dust on the last row of blocks placed in layer one, these need to next to blocks that make up the zig-zag not next to the gaps.
Still working form the front, place a row of eight blocks followed by a row of repeaters and then another row of blocks; the repeaters should face the rear of the CARTS system an be set to the maximum delay. You now need to place redstone dust on the eight blocks that make up the zig-zag, with blocks between the redstone dust in the row towards the front; in other words, one row of alternating blocks and redstone dust and one row of alternating red-stone dust and an empty block. It is on the front of this layer you will place the selection buttons.
At the front of the CARTS system place a two by eight layer of blocks with a row of redstone torches behind it. Then, on the four blocks in the layer below, place a spot of red-stone dust on each. Now place a block in the gaps between these spots of redstone dust to prevent cross talk. If you have done this right up to now, then you should have four lines of redstone dust running down in a stepping line. On the front of this layer you would place signs to let people know where each selection will take them.
Again, working from the front to the back, place a row of blocks. Then a row of repeaters that face to the front of the CARTS system, behind them another row of blocks. The front of this layer is where the indicator lights will go, a row of redstone torches. If you wanted to use redstone lamps as selection indicators instead of torches, replace the repeaters with redstone torches attached to the block near the rear of the CARTS. Then replace the orange blocks near the front of the CARTS with redstone lamps.
Go to the front of the carts system, place a layer of redstone torches on the side of the blocks at the very top. These are your indicator lights. You will probably have three of them on (and two off) when you first place them, don't worry this is because the station has not been used yet. Leave the next row clear for you place signs indicating destination. Next row down, a row of buttons to select your destination.
You have now built your basic CARTS system! Though here are some more steps to help you get your system up and running.
The launch strip
You will need to invert the signal that comes from the line of redstone dust at the front, and send this to a block that has a redstone torch on it. The redstone torch should be under a block with a sloping section of booster track. The torch, and thus the booster, will normally be off, holding the minecart on the slope; when a button is pressed it will turned on for a second or two, long enough to launch the player.