Board Thread:Questions and Answers/@comment-94.156.6.50-20171212184841/@comment-34000140-20180105234134

You will continue to receive random express trains from any prior era. But which type of rail is also random. As AnimePerson1 said, there's no guarantee which type it will be. But a trick I use is to call an express train for each possible rail I have, then leave all the ones still full which I don't want, while clicking on only the ones which I want to be replaced with more of that rail type.

However, keep in mind this applies to Maglev and Hyperloop rail types. Steam, Diesel, and Electric trains all share the same rails (regular). So that trick wouldn't work to get just steam. You can leave something in the Maglev / Hyperloop rails, and hope that the next ones you call are steam.