On the topic of food supply and roads, how exactly does the supply system work? To me it looks like supply lines only go one way, and if this is true is it importance to keep that in mind while connecting cities? For example, would I be able to export food from a city that produces a lot of food too cities that need food by connecting supply lines out from that city rather than into that city?
Also, if I connect a farm to a far-away city will the food production stay the same as if they were close or will food production be slower; and does this also apply to mines and gold?
And one last thing, what does the percent per week number mean when I select a supply line?
Supply lines have a capacity limit, which is changed by distance. That is why you never want your farms connected to far away cities. I've seen it go as high as 100/week along a farm to its adjacent city, but I've never seen higher than 15/week to any city I've connected a farm too (that it isn't immediately adjacent too). I'm assuming that is what you mean by percent per week, although I've never seen any of those values as a percent (could be the software translation error).
As for how it works, it seems to work on two factors, draw and supply amount requested. If I have a city that has reached its requested supply amount all specifically to it will stop until it gets below that supply limit again. Say City A is connected to City B, which is connected to City C. If City A requests supplies, it will take them from City B. City B will feed City A from its store. If the store at City B gets below its requested amount, it will send out a request and pull them from City C. The only thing I haven't check out thoroughly is what will happen if City B wants supplies but City C and City A are below their supply limit?
As for the other factor, draw, it appears that if my cities are supplying garrison troops either inside the city or outside it will attempt to pull supplies up to some amount even if its above the requested amount. I can't figure out anything more than that, just that I've seen my cities have a requested supply of (for example) 1000, and it keeps pulling even above 1000 as long as it has food going directly to troops.