Why did they use vertical trade lanes?

[Lord Caedus]

I imagine from a construction perspective it would be easier to allign the lanes for a distant target if they're oriented vertically, no need to adjust for left/right offset. Aternatively because it makes for easier traffic flow at the enterance/exit points. Ships don't have to avoid turning into each other when you have a multi-lane interchange if your lanes are vertically alligned, they can simply move out of the way of the exit and can shift up or down if they need to without adding extra distance onto their flight path.

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