I believe that they flag the trains to warn them of work being done on the tracks or signals being worked on. Tracks need to be constantly inspected so I believe that they must use flagmen in order to keep the flow moving while still being able to inspect properly
According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 3 words with the pattern F-A-M--. That is, seven letter words with 1st letter F and 3rd letter A and 5th letter M. In alphabetical order, they are: flagman flagmen flammed
According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 5 words with the pattern FL--M--. That is, seven letter words with 1st letter F and 2nd letter L and 5th letter M. In alphabetical order, they are: flagman flagmen flammed flehmen flummox
According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 2 words with the pattern F-A-ME-. That is, seven letter words with 1st letter F and 3rd letter A and 5th letter M and 6th letter E. In alphabetical order, they are: flagmen flammed
According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 4 words with the pattern F--G--N. That is, seven letter words with 1st letter F and 4th letter G and 7th letter N. In alphabetical order, they are: flagman flagmen frogman frogmen
According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 2 words with the pattern -LAGM--. That is, seven letter words with 2nd letter L and 3rd letter A and 4th letter G and 5th letter M. In alphabetical order, they are: flagman flagmen
According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 2 words with the pattern F-AGM--. That is, seven letter words with 1st letter F and 3rd letter A and 4th letter G and 5th letter M. In alphabetical order, they are: flagman flagmen
According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 5 words with the pattern FLAG---. That is, seven letter words with 1st letter F and 2nd letter L and 3rd letter A and 4th letter G. In alphabetical order, they are: flagged flagger flagman flagmen flagons
According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 2 words with the pattern FL-G--N. That is, seven letter words with 1st letter F and 2nd letter L and 4th letter G and 7th letter N. In alphabetical order, they are: flagman flagmen
According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 2 words with the pattern FL-GM--. That is, seven letter words with 1st letter F and 2nd letter L and 4th letter G and 5th letter M. In alphabetical order, they are: flagman flagmen
According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 5 words with the pattern FL---EN. That is, seven letter words with 1st letter F and 2nd letter L and 6th letter E and 7th letter N. In alphabetical order, they are: flagmen flanken flannen flatten flehmen
According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 2 words with the pattern F-AGM-N. That is, seven letter words with 1st letter F and 3rd letter A and 4th letter G and 5th letter M and 7th letter N. In alphabetical order, they are: flagman flagmen