Railroads by Traders

Your trader will create Railroad once you have reached the technology required (Steam Power). Does not consume/require Coal or Iron. Your roads in your territory are also upgraded once you reach Modern Era AND have researched the technology. NOTE: your roads will be upgraded into Modern Road if you haven't researched Steam Power when you enter Modern Era, and you have no chance to upgrade them later unless you use Trader or Military Engineer. Tested for Persian: if you reach Modern Era without the technology: your roads will be upgraded into Railroads and your Traders can create Railroads INSIDE YOUR TERRITORY. Outside of it, Modern Roads.