Accelerator
The Accelerator is a utility block. It speeds up entities that pass on top of it, making it a great tool for creating fast travel systems.

Crafting
To craft an Accelerator, you need four Arrow Signs, four iron ingots, and one lapis lazuli. Place them in a crafting table like so:

Usage
Right-clicking with the Accelerator in hand will place it in the world. The Accelerator will speed up entities that pass on top of it.
It is slippery, meaning entities will slide on top of it. The Accelerator will speed up entities by a factor of 120% (1.2x). You can place multiple Accelerators in a row to increase the speed further.
The Accelerator can be broken with any tool or by hand. Breaking it will drop the Accelerator as an item.