First time playing as Iroquis and noticed that after you research Railroad any forest tile that is inside your border acts as railroad connection. It still doesn't let you move on them as they would be railroads but they will connect your cities giving the Railroad bonus to production in the city. In the safe city of Argungu is not connected with a railroad but is connected by forests to another city that is but still has the production bonus. This might work as designed but the description of the The Great Warpath special ability it doesn't mention anything of the trade connection to give the railroad bonus too after the Railroad tech has been researched. The save can be found in this thread as it doesn't let me upload the same save again.