Sorry but trucks will always make more money, and buses. The expense to run a train, anywhere from 500k+ makes your profit margin vanish. Trucks cost less to transport cargo and do it in the same time and more frequently, without the huge running cost.
This can also be said for transporting via a bus from town to town, vehicles are just better to use over trains in this game. Which in itself is ironic since the games name is “train fever”.