If you are into train games and have not heard of Derail Valley, give it a try!

It is an incredibly realistic simulation of cargo train driving, either between stations or as a shunter within a single station. It can be from really relaxing, when picking a task that is well within the specifications of the locomotive, to very challenging when driving the locomotive at its limits. They currently have six different locomotives that have vastly different characteristics, including various diesel and steam engines. I have played some 15 hours so far and am really loving it.