It happens so that if there are two raw material providers A&B both provides to same two factory C&D, raw material makes long tour
disturbing stable supply to factories.
However, this can be avoided by making extra station at raw provider
and factory. Using one as supply only and one as depart only(at factory station). On raw provider side, one for factory C and one for
factory D.
This is unintuitive to have to build two station.
(putting aside real world example but as game)
Maybe there could be a order at scheduling to make
convoy pickup only and deliver only at specific station.
If we could specify which cargo, even better.
(especially at later game stage)
Would enough people find this useful?
I find that it makes perfect sense to gather freight at one point and to distribute it to various consumers either through a central hub or making the convoy stop at both destinations.
If you want to reduce the amount of lines, you can do (supply A to supply B) then (supply B to factory C to factory D) or don't bother to cross connect the supply chain at all and simply do (supply A to factory C) and (supply B to factory D).
some factory chains are complex and it's better to have all supplies sent to a central hub.
Its hard to use hub when Raw-Factory-Raw line is 180 degree (straight line).
Other than that hub should do.
It will be still hard to have control when same cargo type transports many
different type of products.