For very large networks, the goods and passengers should be collected at a hub, if you want a effective transport flow. For passengers, buses should bring them to hub train/tram/ship/airplane stations for further travel. That way, every vehicle is used in its part for the share revenue. Also, goods should be brought by trucks/trains/ships/airplanes from different resources/industries to a common truck/train/ship/airplane station, if the goods amount is low on every of the resouce/industry, they are collected and transported further on a high capacity truck/train/ship/airplane. This is only useful in a situation, when goods/products are collected from a short route, and then transported to a long route. This increases unnecessary traffic, and avoids gridlocks, and also increases the amount of cargo transported per convoi, this increasing profit quicker.

Only full convoins bring maximum profit. It does not matter, if a link in this hub chain is negative, as long as at least the common truck/train/ship/airplane of this hub chain is making profit. In this case, it is really BIG profit. It is advised, to maximize transport performance, to use low capacity vehicles (trucks), to collect goods, and bring them to the hub train station. The train could, depending on the wished layout, either bring the goods to the consumer, or you could have the train/a few trains go to a hub ship station (if overseeas), and the ship brings the goods on the other side, where again, there might be either the consumer, or a train/truck takeover.

With passenger hub layouts, it is possible to do the same, just replace trucks with busses/trams/monorail... A hub can also be combined, of course, meaning, it can be a passenger/good hub at the same time. Or even an underhub of a greater hub.

The planes are not really required for goods, but for passengers. At the moment, they are not necessary, only a decoration, but can be handy as end vehicles of a passenger hub chain (like the planes in real life, people travel by plane), but only to connect two remote destination hubs. This way you get maximal profit from them, considering their price.

Using the hub technique, you get even an automatic redistribution of goods, because the AI internal goods routing algorithm works splendid, and will automatically reroute goods, if they share at least a part of a route in hub. Be careful though! Here is a little catch. If you participate and plan a route and bring the passengers/goods to a hub, the automatic AI algorithm may choose an other route, if there are other shorter connections for that passengers/goods destination. Always control, as much as you can. It can get very difficult for big networks.

Hubs bring an other advantage : You have the overview of goods from one single starting point, and also if one route brings loss, some other could bring more profit. In large transport networks, it is mandatory to have more routes which bring profit, and few losses. Ideal case is that all constantly bring profit, which can only be achieved by using effective hub layouts.

Example hub chain layouts :