I'm working on a map showing oil shipping. Basically, I have a a series of nodes/line segments that make up the shipping network. I've joined the sums of oil that traveled along each node, so can show how much oil is traveling over those nodes.
How can I show the directional breakdown along each node? In other words, I'm trying to show the split each segment by the direction of the oil on it, showing that with different colors and having the pen width adjust to the size of the flow in that direction.
Edit: Could this be done with two layers, one of which is given a data-defined offset based on the width of the other layer, such that they line up with eachother?
Multiple layer version: