Fun idea, and love the style. I did find it hard to judge the distance to the towns, and frequently just missed them. I feel that the time limit also makes it hard to really test large trains; I got five cars at the end, and no more.
I would definitely like to improve those. A warning sign would be cool, and I think that I'd like the player to try and reach a certain amount of winning money via a big train instead of having a countdown.