Trade routes maximum distance?

[Ticio]

Hi everyone!

I was playing a game and the map was constituted (more or less) of 2 big continents and some tiny islands. My Capital was a coastal city in the "southeast" corner of one of the continents. To the righ, just a lot of water and just a moderately big island in the center (you could have 5 cities in horizontal disposition), then a lot of water until you reached the second big continent.

As I was looking for trade routes for City states (Owls of minerva) I founded a city in the big second continent and another coastal city in the "midle island" to ensure that my trade routes could reach the cities.

After ending the trade route Capital > City in "Middle island" to be able to send to trader to the second continent I discover I did'nt pay attention and the second continent was located at more than 30 tiles. Therefore, the trader could not reach the city in the second continent.

Therefore, I had to put another city in the right part of the island to reach the 30 tiles. The problem? the island was already occupy by one ally.

My ally’s cities were not coastal (AI), so my trader could not go through them and then change to water tiles so I had to make all my traders go to the other continent through the West and took too many turns to be able to compete for the city states I wanted.

After this convoluted history (sorry), I wanted to ask some questions:

1) It is possible to make a trade line go through more than 15/30 tiles of distance? I know that a trade post gives you that power, but could I have done anything in my scenario without founding new cities?

2) If I have a game where I spawn in an island of 1 tile and the next island is at 31 tiles, this city will be forever banned to trade?

3) If i have an inland city, but I'm able to make a Port district, can the traders go through it to become aa naval merchant or is mandatory to have the city as a coastal city?
(I'm currently doing the experiment but I'm sure asking is faster )

Thank you very much as always!

 

[Linklite]

1. The only way to extend routes is by trading posts. By what you've written, it's unclear if you understand that you can set up trading posts in other Civ's cities. You could have set up a trade route to your ally's city, then when it was done, you would have had a grading post there, the same as if it had been your city. It's not quite ideal; if your relationship soured and war broke out, your route would be threatened, but still.
2. To my understanding, yes. That sucks. But I'm not sure that would ever happen - 30 tiles is a very long way, to not have any island whatsoever within 30 tiles in any direction is unlikely, if it's even possible using the random maps.
3. I believe.you must need a harbour, thencity centre doesn't directly factor into it. Might be wrong.

 

[Ticio]

1. The only way to extend routes is by trading posts. By what you've written, it's unclear if you understand that you can set up trading posts in other Civ's cities. You could have set up a trade route to your ally's city, then when it was done, you would have had a grading post there, the same as if it had been your city. It's not quite ideal; if your relationship soured and war broke out, your route would be threatened, but still.
2. To my understanding, yes. That sucks. But I'm not sure that would ever happen - 30 tiles is a very long way, to not have any island whatsoever within 30 tiles in any direction is unlikely, if it's even possible using the random maps.
3. I believe.you must need a harbour, thencity centre doesn't directly factor into it. Might be wrong.

1. I knew this was a way, but I was wondering that maybe others existed and I wasn't aware. So I'm affraid not... As the ally was de AI, he never made any port district so it was impossible to send trade routes through his cities

2. I hope it never happens to me the question was to make sure not other ways of increasing trading distances existed (apart trading post)

3. I just checked it today! Yes, even if the city is not coastal, as soon as you add a port district traders can change water tiles for ground tiles and vice versa!

I would have a last question;

4) It is totally impossible to change the efficiency of the trade route?

I mean, I for sure cannot choose the way it goes (i cannot choose the tiles the caravan will traverse), but if I improve the path (for example I make a railroad or a mountain pass) the game will change the path automaticlly, or the trade path between these two cities will be always the same?

EDIT: After some tries, yes, the commercial routes change to a more optimal one (even if they were done before).