This goes back early 1900s I imagine. In this NYTimes video (2'05'') there are five men on a railroad equipment. I tried looking for pictures and on americanrails.com, but found no clue to get to the name of that kind of workers and to the thing they are giving motion to.
1 Answer
That is a handcar, specifically one with a pump. Here's a video about how one works.
It would normally be operated by railroad employees, but in that specific video they appear to be police officers, or potentially private railroad security.