
It can also be used to evenly load a two-sided belt onto the side of one that already has items on it:

Faster belts can be used appropriately to maintain throughput. If anybody can improve this or already knows of another version, I'd really like to see it. I'm trying to find a more compact version. My real goal is to balance the two input lanes regardless of which output lane is backed up (when both lanes are saturated), but this is good enough in most of the situations I need it in.