NY Marathon has rules about the number and speed of runners on the Verrazano Bridge- at the start of the race. So the is something to it.

I have shot off a note to Army pal for clarification on present practice ...back atcha' when I get an answer. He's used to my whacky questions.
wow
EDIT : about 4:45 p.m. EDT
My Army chum says : "I have never read anything in any manuals, I know that it isn't in FM22-5 (Drill & Ceremony).