Next add a nurbs curve in the correct place and set it up to your liking. Parent your emptys to the path using offset for the cars and curve follow etc. This is all described in detail in the 2.3 guide or the wiki. Advanced blenderheads can use this same path and dupliframes to place signals or telegraph poles etc. And I used the new curve deform parent to get the track to lay correctly as well.You need to get it right now as this path will be almost impossible to change later.The set up when you advance through frames or use alt-a should look and behave like a train.Dont worry about speed at this stage.You will probably need to adjust the path length depending on your track.I also turned off gravity in the world buttons as this is not needed.It made it a bit easier for smoke and effects.