Question: One of my British ancestors was a signal man on one census and previously a Railroad Policeman. Was he a security guard at the railroad station in the 1860's?
Answer: Even though these sound like two occupations they are one in the same. The older term once used for a signal man on the railroad was a railroad policeman. See the reference stated on Wikipedia - http://en.wikipedia.org/wiki/Signalman_%28rail%29