I assume you are talking about train employees. Many of my ancestors worked the trains. According to the records I found for my people-one railroad used the name PORTER, as a generic name for colored employees no matter if they worked the tracks or on board. He worked for the Terminal Railroad. Those jobs weren't always safe. Black men were hired to be porter on board, mainly because they were used to the slave way of life and would do what the white passengers said 'without question', on threat of loosing their jobs. There are many stories. I suggest you go to the Pullman Porter site. Read about their history. If you know where your ancestor's permanent home of record was, look for the railroads that came through his area. If you have found him on a census as occupation porter, start with the earliest year you find him working the trains.
Also if your ancestors lived long enough to draw a pension for the railroad, for a fee, you may be able to get a copy of his records. In my case 'those records of my parternal grandfather, just happened to get destroyed in a major fire, the year before I was inquiring.' Yeh Right!! Good Luck