Hi @bloomlwold - If you're playing the Discovery Delta region and trying to send anything (passengers or gifts) by rail between Huckleberry Island and Sawyer's Crossing, it will never work because of a major design flaw. Those two cities show a rail connection and are supposed to be connected, but someone on the dev team must have forgotten to connect the tracks to a bridge - the tracks just stop at the edge of the water on both sides. It's been that way since the game launched in 2013 and they never fixed it.
If you're sending resources via rail on any of the other cities that have a railway connection, then the basic resource gifting rules apply.
- Both cities have to be in the same connected group, generally the group of 4 that shares a Great Work. It has been my experience that if you try to send a gift from a city to one that is not connected, it should give you an error or not allow you to select that city for gifting (so that you don't lose the resources)
- Both cities need a trade port with rail terminals and a storage lot for whatever resource you're shipping. (I know you said you already have this, but I mention it in case it helps someone else reading this)
- Set the resource options in the trade port Global Management tab to either "Use Locally" or "Import"
- When you send the gift, let the sending city run long enough to see the message that the gift has been sent, and watch the resource to make sure the entire gift has shipped
- After the gift has been sent, save and load the receiving city and wait for the delivery
- One of the two cities must have at least one delivery truck garage - it doesn't have to be in the railway trade port, it can be in any trade depot.
- There is no way to force the gift to be sent via rail.
Researching your question, I've played a few different scenarios now, trying to force the cities to use the train to deliver the resources. I can't do it - if I remove all of the trade depot/port delivery trucks from both cities, the gifting city will not send the gift. Even though I have the train freight terminal set up and everything should work, it doesn't.
The really strange thing is that I can bulldoze all of the delivery truck garages from the sending city, and just have 1 delivery truck at the receiving city, and it will still send the gift. Sometimes it will choose to send it by train, sometimes it will send it by truck, and sometimes it will send it by both. And - it doesn't seem to matter what way it sends the gift in the gifting city, when you load the receiving city, it could be delivered the same way or it might be delivered a different way. If I send 10 tons, it usually sends it by truck and receives it by truck (the trucks can only hold 10 tons each). But let's say I send 30 tons - I might see a truck leave with 10 tons and a train leave with 20 tons. Then, when I loaded the receiving city, it might deliver all 30 tons by 3 trucks.
So, even with deliveries by rail, you'll also need to have at least 1 delivery truck somewhere in one of the two cities. It did seem to me that I could get more deliveries by train if I was running other trade depots (with lots of delivery trucks) and did NOT have any trucks at the train depot. The other delivery trucks might still be used, but more often than not it would choose the train in that scenario. It's very frustrating and highlights another major bug with the regional sharing. The connections aren't really "connected", each city initiates the transaction separately.
I hope that helps - I wish there were a way to force the cities to use the trains, but there doesn't appear to be.