Hi,
Welcome to the forum.
Please read the first post in any forum entitled how to use this forum.
http://forum.arduino.cc/index.php/topic,148850.0.html
I assume you have the Arduino,what model?, monitoring the voltage going to the track.
What scale railway?
What track controller are you using?
What type is it?
Depending on its construction there may be an easy solution.
Can you please post a copy of your connection circuit, in CAD or a picture of a hand drawn circuit in jpg, png?
Showing your power supplies, controller, Arduino and track connections.
Thanks.. Tom.. 