Transport Networks Defined

[Eric Snyder]

** I have updated this from the first posting, including information gained from feedback (thanks!). **

I noticed in my games that the behavior of trade networks did not seem to conform to the definition given in the Civ4 manual. Here is what the manual says:

.... A city will get the benifits of an improved resource if that resource is within the city's "city radius." If not, the improved resource must be connected to the city by a "transport network" of roads, rivers and coastlines for that city to gain its benifits.

This description is ambiguous and incorrect (e.g. city radius). After doing some testing, I have come up with a new description which may serve you better:

A city will get the benifits of an improved resource if that resource is within your borders and is connected to the city by a "transport network". This network must be able to trace from the resource an unbroken path of roads, rivers, or any combination of roads and rivers back to the city.

Cities may be connected to other cities by any combination of roads, rivers, and (conditionaly) coastal waters. Before the Sailing technology is researched, coastal waters may be used in the transport network only if they are within your borders. While rivers and coastal waters "connect", roads and coastal waters do not. Fresh water lakes function the same as coastal waters.

A transport network's roads, rivers, and coastal waters (with Sailing) may be traced through another civilization's borders (with or without an Open Borders agreement) if you are at peace with them. A state of war will block this path.

A city that is built atop of a resource will gain access to it only if your civilization has the technology to build the resource's required improvement. You can not actualy build the improvement, but you will automaticaly gain the benifits of the resource.

At the bottom of this post I have included an updated map showing transport network examples. Following is a description of it:

The civilization shown does not have the Sailing technology.

• Pig w/ Pasture is connected to City A (road -> river -> City A)
• Sheep w/ Pasture is connected to City A (river -> City A) *note that no road is required on the resource tile if the resource is adjacent to a river.
• Wine w/ Plantation is not connected to City A (it requires a road).
• Cow w/ Pasture is connected to City B (road -> City B)*notice that City A traces a path of river -> coast -> road/cow, but because roads do not connect to coasts the network is incomplete.
• Corn w/ Farm is not connected to City C (the corn is not within the civ's borders).
• City C is connected to City B (coastal waters within border), thus City C receives the Cow of City B.
• With the advent of Sailing, all of the cities would be connected (City A -> river -> coastal waters -> Cities B & C)

I hope that you find this useful.

[DeepO]

Maybe it would be easier to explain if you would also add a list of what you get in each city, and how you connected everything. e.g. the deer looks to be unconnected, no wonder you won't get the resource.

DeepO

[Eric Snyder]

This race has the Hunting and Animal Husbandry Techs.

The Pig with Pasture is connected to City A via a road to the river to City A.

The Sheep with Pasture (no road) is connected to City A via the river to City A.

The Deer with Camp (no road) is NOT connected with any city.

The Cow with Pasture is connected to City B via road. It is NOT connected to City A.

The Ivory with Camp is not connected to any city.

Once this Civ gains the Sailing tech, both cities with share thier resources with each other via the coastline (City A -> river -> coast -> City B).


The cow really has me scatching my head. It is not within any city radius, but it is within the cultural border. I wonder if this is indeed a bug...

Rivers seem to function exactly like roads for connecting purposes, although if a resource is adjacent to a river (the sheep), then the resource does not need a road build atop of it. If the resource is adjacent to a city (the deer), then it DOES need a road built atop of it.

Lakes do not seem to effect trade networks in any way. I would have guessed that they would have worked like rivers.

Coasts only connect cities (with Sailing tech). Resources adjacent to coastal tiles do not gain connection from the coast alone (coasts do not act like rivers).

I hope that this helps.

Eric

[Eric Snyder]

Sorry DeepO, but I do not know how to post an image in between my post, so I had to post the picture, then write the message...

Eric

[DeepO]

Originally posted by Eric Snyder
The cow really has me scatching my head. It is not within any city radius, but it is within the cultural border. I wonder if this is indeed a bug...

Bug? how so? it is within your borders, and connected to city B by road. Is not connected to city A... so B gets a cow, A doesn't.

the manual should read

A city will get the benifits of an improved resource if that resource is withinyour borders. The improved resource must be connected to the city by a "transport network" of roads, rivers and coastlines for that city to gain its benifits.

BTW, you can check up on trade networks in globe view if there is doubt.

DeepO

[Eric Snyder]

Sure, the word bug may have been overstated. I guess that it was just behavour that I did not expect. Still stuck in the Civ3 mind set...

Your manual clarification is much improved over the original, but I think that I would clarify it even further. How's this?

A city will get the benifits of an improved resource if that resource is within your borders and is connected to the city by a "transport network". This network must be able to trace from the resource an unbroken path of roads, rivers, or any combination of roads and rivers back to the city. Cities may be connected to other cities by any combination of roads, rivers, and coastal waters.

[Andrew1999]

Cities can be connected by coastal waters without Sailing if there is a route that can be traced between the two that is entirely within your borders or "territorial waters." On your example, if you place City C on top of the Cow, all three cities would be able to trade by sea, even with no roads and no naval techs, since there would be a contiguous block of controlled coast tiles along the south and west coasts. It took me a while to figure out how some of my coastal cities were connected when I first started.

[kimmygibler]

So if the resource is in the city radius, does it need to be connected to the trade network?

[Eric Snyder]

So if the resource is in the city radius, does it need to be connected to the trade network?

Yes, a resource must always be connected to a transport network to be of use.

[Eric Snyder]

Cities can be connected by coastal waters without Sailing if there is a route that can be traced between the two that is entirely within your borders or "territorial waters."

I just tested that and you're right. Thanks for the tip!

[Falconer999]

In my last game, I think I noticed a little discrepancy with the AI and the way resources work. I had cows in a tile adjacent to my city and had a worker doing auto tile improvements and then auto trade improvements.

The worker built a pasture on the cow tile, but did not build a road. It did build roads to a mine and a beaver camp 1 square out from the city.

After the worker had 'finished' doing everything it could, it went back to the city and just sat there. It never went out and built a road to connect the cows. I did not get any benefit from the cows. I manually made the worker build a road on the cow tile and received the benefit.

Does the AI think that tiles adjacent to a city are connected even though they aren't?

[Eric Snyder]

Ah, there is something else that I should add. If you build a city atop of a resource, then the city will automaticaly gain access to it if you have the technology to build it's improvement. You can't actually build this improvement, so you will not get the food/hammer/coin benifits of it, but you will get access to the resource (including the happiness or health benifits).

[Tennyson]

you will not get the food/hammer/coin benifits of it, but you will get access to the resource (including the happiness or health benifits).

I'm not certain this is true. I had a game where I built one city on a horse resource, and had another connected and pastured; in trading with AIs, only one horse asset was listed.

[proviisori]

Originally posted by Tennyson
I'm not certain this is true. I had a game where I built one city on a horse resource, and had another connected and pastured; in trading with AIs, only one horse asset was listed.

IMO that's right. You are using one horse for your purposes and then you have a extra horse resource. The extra horse is up for trading.

If I have understand correctly. Your civ will reserve the only resource of particular kind for itself and the extra ones are tradeable.

[Tennyson]

IMO that's right. You are using one horse for your purposes and then you have a extra horse resource. The extra horse is up for trading.

If I have understand correctly. Your civ will reserve the only resource of particular kind for itself and the extra ones are tradeable.

It should work that way, but at the time it listed everything I had as available to trade as (1). The only other thing I had two of was Stone, yet corn and rice and cows and etc. were all listed. And stone was listed as (2), not (1).

It should be easy enough to verify, but until it's verified I do not trust the trade screen NOT to let me trade away my only copy of a resource. Because that's what it's looked like in the few games I've played.

I would definately prefer if I only had one of something that it not be listed.