"Road guards" - these people were designated members of a flight* and ran out to stop traffic in all directions when the flight had to march across an intersection. If I remember correctly, there was no singing when crossing the street. Possibly this was to avoid irritating halted drivers any more than they already were by having to wait, possibly to allow the road guards to hear commands.

To Mac: the singing/marching and cadence calling is something that still survives today with no regard for collectors or folklorists. When I was in basic (I know, it was a bazillion years ago) each flight had to come up with its own song. They wrote, stole and adapted or just plain stole. Ours was "If they could see me now, that little gang of mine, wakin' up at dawn and marchin' in a line" etc. The whole flight learned it and sang it as we marched to our graduation.

The Air Force doesn't sing much as, once out of basic and technical training schools, there isn't really any marching. The Army and Marines however, do. I was in Kuwait with a collection of units, and would walk to the bathrooms in the morning and be passed by various units doing PT, all singing their OWN songs. I would have loved to collect them, but it would require me running behind them with a recording device, holding a microphone. That wasn't going to happen.

The point is that you can write your own song. You can take an existing chant or song and change it or you can write a whole new one. Get the guys in the unit to help - they just need pairs of lines that rhyme all fitting the same rhythm. That's what military units do.

* Flight in the Air Force, platoon in the Army and I don't have a clue about the Navy.