Anyone know how these work exactly?

It seems like the amount of commerce you get depends on the size of the city you are trading with, +bonuses.

But in my current game, most of my cities have national trade routes. And it seems I can only have One trade route to each foreign city in the nations I have an open border with.

I'd like to learn more as well. In my current game on an Archipelago map, the Trade Routes were to be part of my strategy. I built the Great Lighthouse and researched the techs to trade across the oceans. I built Harbors and I learned the +1 TR techs. Things were looking good enough to support some piracy. So I sent out some HN ships and units and got busy with it. Meanwhile I built Inns and Taverns to further capitalize on the routes. But it was then that I noticed that most every foreign trade route had ceased. I had open border agreements with 2 other civs and had gifted them tech to preserve good relations. But my routes went down from 6 and 7 to 1. I've noticed this before. So it wasn't my pirates that did it.

I wonder if I lost the trade routes because these civs had begun trading with other civs. And even though I'm the GDP powerhouse this game, they traded with lesser economies instead. Perhaps all of the trade route slots for each city only work once and AI prefers to trade to AI? Maybe GDP has nothing to do with it? Or maybe it is relations based?

Yeah, the trade route mechanics are quite confusing sometimes. I would really like to know more about it. Counts one trade route as an input and an output channel or is it for a city totally irrelavant if another city is capable of supporting one more trade route to it to enable trade income for the first city? How does a city chose its trade partners ...

read through this thread. it should help.
http://forums.civfanatics.com/showthread.php?t=159047

I'm pretty sure there's no new code for ffh in this regard.

Thanks Thonnas, I'll read that when I get some time over.

Very interesting and revealing thread link, Thonnas. Thanks. Now I got it.

It seems like the amount of commerce you get depends on the size of the city you are trading with, +bonuses.

I believe distance may be a factor also.

But in my current game, most of my cities have national trade routes. And it seems I can only have One trade route to each foreign city in the nations I have an open border with.

This may depend on the fact that the foreign cities did not have enough trade routes available to trade with you, ie. they didn't build Lighthouse, Inn, etc. etc.

I believe distance may be a factor also.

Distance is definitely a factor. In the thread Thonnas mentioned they figured out the complete formula.

This may depend on the fact that the foreign cities did not have enough trade routes available to trade with you, ie. they didn't build Lighthouse, Inn, etc. etc.

No, national and foreign trade routes are handled differently. Every foreign city of a nation you have open borders with will be available only once for your whole empire. It's totally independent of the number of trade routes the foreign city can handle, because trade routes are always one way. Means, if your city trades with another city it doesn't imply that the other city is also trading with your city.

Is it possible for foreign religions to spread to your cities via only river trade routes ? In one of my games I felt attacked - before I could even whip out a missionary of my own .... Why India ... Why ? :crazyeye:

I think you may be in the wrong forum. There is no India in this mod.

the answer to his question is yes, btw.