I don't recall every seeing a hay trailer with any type of rear lighting. I believe, technically, here in Missouri if the trailer is being pulled by a licensed vehicle it must meet the standards of that vehicle. If it's pulled by an unlicensed vehicle, a tractor, it is exempt. One time I bought a small pole building and moved it on a State Hiway, about 3 miles. I asked the Missouri State Hiway Patrol what permits or lighting I needed to move it. The Officer asked me what I was going to pull it with? I said my tractor. He said you don't need anything as it's considered AG equipment. If you hitch it to your truck then you'll need permits and special escort lighting. Go figure. Early on a Sunday morning we moved it with the tractor. Had a vehicle ahead of me 1/4 mile with flashers on and a vehicle behind me. I didn't have any sharp hills to go over and could always see the escort ahead of me. I drove down the middle of the road with a 26ft wide building on wheels. When I turned off the hiway there were 2 cars stacked up behind me, didn't meet anyone.