A Limiter Rail simply limits the speed of a cart going over it to a speed where the cart can be stopped by a single (unpowered) Powered Rail. This can be used to make sure a cart stops right under/above a Hopper, for example.

By powering the rail with redstone, the braking is suppressed, and the rail acts like it is a normal rail.

[crafting{200, 110, key=block/limiter_rail}]