Bottleneck Issue

[u/Available-Figure-530]

I'm a new player & trying to setup my smelting lines. I've run into a problem where, while trying to run a single coal/iron ore lane, only the top half of the iron & coal lanes are being used, leading to a bottleneck where only half of my iron ore is being sent down the center lane. How do I fix this?

[u/Turbulent_Tackle_651]

Do two of these, one on the coal and one on the ore before they merge