Took some time to fully be immersed into the drama, not sure what it is, but I found it hard to feel any excitement or thrill when watching Train, feel like it's a combination of the actors/actresses, lack of supporting roles and very weak villains.
To give it some credit, it does have a very different feel compared to other time travel type of k-drama thrillers. At first, I was going to say the plot was too predictable, but after finding out who the villain is, that changed my mind completely.
Overall, I would recommend this drama, as it does establish it's own type of style and quite unique compared to rest of the similar k-dramas such as Tunnel and Life on Mars.
[Update] Finished watching and completely shocked how bad the final episode was, literally fell asleep halfway through, not sure if I was too tired that day or the story was super boring. I do not recommend this drama anymore, tried to give it a chance, but it failed me in the very end =/