Good point on the irreg cart and no flashers. I would assume its a if you have it then you must use it. This is UPS so who knows? We all know that UPS will just use those rules to blame a operator in the case of an accident anyway.Well, the DOK says when operating yard vehicles. I believe it refers to yard birds, tugs, irreg carts, not to tractors or package cars. They need some way of being seen in the yard.
Here, it also says "yard vehicles must be equipped with operable headlights, hazard lights, or reflective material in order to provide 360 degree visibility," meaning any one of the three.
The proof is that our irreg carts that are authorized to drive in the yard have only a headlight. No hazard lights or reflective material.
Like I said, just my opinion.
Here, the procedure is to use 4 ways only while backing and there is no procedure for using headlights while in the yard. I just find headlights blinding and annoying and 4 ways confusing if used all the time.
If it is different there, that's OK.