Note: This design will likely be broken in 1.11 because the piston translocation bug was fixed.

Here is a fairly simple, very fast, and infinitely expandable horizontal player transportation. It abuses a bug introduced in one of the 1.9 snapshots (this bug does exist in 1.9) involving pistons. If you are standing in an extended piston head, when the piston retracts, you go through the piston, and you go behind the piston, having moved 2 blocks from where you started almost instantly. And due to the way this concept works, it is easily expandable. I think the speed is 20 m/s. Not the fastest form of transportation in Minecraft, but certainly one of the faster ones. This design is 9 wide, 41 deep for the design expanded to 40 blocks (or 42 deep if you count the space where the player is after the player gets to the end), 2 high (or 3 high, if you count the space required to be air so the 2 high player can fit).