Unbalancers
From #openttdcoop wiki
NOTE: This page is not final yet, so it might look messy and contain incorrect information.
Unbalancer
Overview
The Idea behind unbalancers is, that you want to keep the traffic on 1 lane while the second lane is as empty as possible. The principle is called SML.
Simple Unbalancer
Unbalancer with Bypass
Sometimes trains turning off have to stop because a train on the other lane is coming, therefor a bypass is needed to keep the flow flowing.