Harbour vs Road/Railroad - Trade route question

Hypotentical question:

Let's say I was connecting City A to City B early game with roads. Later on, I decide to put a harbor in both.... which in fact nets more gold per turn in trade route than the original road between City A and B.

Will I get paid the new improved trade route amount from the harbour? Or, will the game keep the original low paid trade route with road/railroad? Just wondering...

Cheers

Last I saw them the formulae for city connection gold weren't affected by how the connection is made. IIRC they're only a function of the size of the city and the size of your capital.

Haven't tested in a long time but last time i tried a similar scenario.i.e. connected a city by a road initially then built a harbour and decided to delete the road there seemed to be a bug in it recognising the harbour as a connection after deleting the road.

As TyBoy mentioned though gold generated is equal however the connection is made and the only advantage for a harbour really is that it usually costs less to maintain than the road, certainly if it replaces a railroad so you will net more gold via a harbour than by a road because it will cost less to maintain.

Right, gold is tied to city sizes, not the kind of connection. A harbor costs 4gpt, so technically, as long as your cities are 5 tiles away, a harbor gives you more gold. (If you don't have any discount on roads) - it also adds the railroad-bonus as soon as you have the tech, so you not only save some additional maintenance, but you also get it quite a few turns faster.

However, it comes with some downsides. It doesn't give you the mobility to defend your empire like roads do - and you need to defend it, because your harbor-connection breaks if enemy ships block your harbor. So if cities are on the same continent and reasonably close to each other, a road is usually the better choice.