Pipe/Belt Upgrade - Two-Lane
Make an additional upgrade to pipes / belts.
The additional upgrade to all 3 existing size updates should be that you can add a second lane in the same space.
The so created two lanes should be adjustable in direction.
Probably it would need an entry and exit building or some other idea (preferable just to be able to attach and select the line) so it can be accessed at each ends by two lines.
I find it quite a struggle in the late game to place all the pipes / belts.
With this upgrade it would double the capacity of all the lines.