Traffic Light

Im wondering if there is a certain intsruction on the pattern that traffic light for trains are suppose to go im working on a good size rail yard and cant find anything as far as rules go, can anyone help

There are several good threads and sites on signaling that you may be able to locate by searching here or on the web by ding a "Google search " for railroad signals/ing. The types used are varied and are railroad specific for a large degree. More and more I think that signals are being replaced/suplimented by radio dispatching. Good luck on your quest!
Will