Here is an trainsetup for the Blender Game Engine i made yesterday, it is based on Steering Actuators. It´s an easier way to animate your train in the Blender Game Engine :) . For a better understanding of the technique I used, I have marked the different railway carriages with number.
<img src="http://3dartdh.files.wordpress.com/2013/03/trainsetup_for_bge_2.gif?w=352" alt="" />
You could adjust the speed of the carriages in the logic editor , each railway carriage has a Steering Actuators and there you will find the velocity setting in this demo, the velocity is set to 20.
Here is a short demo video:
A illustration about the Logic-setting:
<img src="http://3dartdh.files.wordpress.com/2013/03/trainsetup-for-bge-demo-info.jpg?w=917" alt="" width="917" height="458" />
Have fun with it :)