The only manual I've been able to find (by accident actually just last night) was a small button in the game itself under one of the menus. Its just an html file located in the game directory itself.

Luckily I played the original American release of a-train back in 1993, so I had a good idea of what to expect. But this is that game on steroids. I love every bit of it. My only complaint is it can be cumbersome to set up vehicle schedules with any ounce of complexity. And I still have no clue how to use dead head schedules or train sheds. The tutorials are great at teaching you 95% of the game. The other 5% are mechanics hidden behind the scene.